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- Best flask: At a glance
- The best flasks to buy in 2024
- 1. Thermos Direct Drink Flask 470ml: Best flask for commuters
- 2. Hydro Flask Standard Mouth 21oz (621ml): Best sports flask
- 3. SIGG Hot and Cold ONE: Best cheap durable flask for hikers
- 4. Thermos King Food Flask 470ml: Best food flask
- 5. SHO Food Flask 530ml: Best food flask for the style conscious
- 6. Contigo Autoseal Chill water bottle: Best flask for cold drinks
- How to choose the best vacuum flask for you
While Thermos may be a well-known and generic term for a flask, it’s just one of many brands. In fact, the best flasks come in all shapes and sizes and under many names. Our recommendations below have managed to master the art and science of the vacuum flask – that ingenious, insulated container that does the job of a portable kettle or fridge without the need for a plug socket.
Whether it’s a chunky “food flask”, sleek “vacuum bottle” or something in between, the job of a flask is to keep food and drink hot or cold without leaking, all day long. Some of the winners on our list can insulate for more than 24 hours, which is long enough to survive the toughest hike or most gruelling commute.
For this article, we’ve picked out several flasks that excel at insulation, leak-proofness, durability and, of course, value for money. Before you scroll on, take a look at our buying guide below for some helpful tips on buying the best flask.
Best flask: At a glance
| Best food flask | Thermos King Food Flask (~£25) | |
| Best flask for cold drinks | Contigo Autoseal Chill (~£25) | |
| Best flask for commuters | Thermos Direct Drink Flask (~£22) |
The best flasks to buy in 2024
1. Thermos Direct Drink Flask 470ml: Best flask for commuters
Price when reviewed: £22 | Check price at Amazon
- Great for… Packing in your bag for work
- Not so great for… Sheer insulating power
At the other end of the weight spectrum comes this gorgeous newcomer from Thermos, weighing in at barely more than 200g (before there’s anything in it, of course) and topped with a ‘direct drink’ spout that’s perfect for the train to work.
Thermos designed the flask to be as light and ergonomically comfortable as possible, with a cool sweat-proof exterior. It can’t match the Stanley Master for sheer insulating power (no flask can, to be honest) but it still does a great job of keeping cold drinks cold for a couple of days, and hot drinks piping hot all day.
Key specs – Material: Stainless steel (not officially dishwasher-safe); Capacity: 470ml; Size: 22 x 6.5 x 6.5cm; Weight: 210g; Colours available: 1
2. Hydro Flask Standard Mouth 21oz (621ml): Best sports flask
Price when reviewed: £35 | Check price at Amazon
- Great for… Keeping iced drinks cold
- Not so great for… Price
Keep drinks cold in the blazing sunshine with this stylish, lightweight, double-wall insulated bottle, made from sturdy stainless steel and a powder-coating finish to stop it slipping out of sweaty hands. It does keep hot drinks hot for 12 hours, but it’s on summer adventures that this flask really comes into its own, keeping iced drinks cold for more than 24 hours.
Hydro Flask also comes in a smaller 12oz version and in a ‘wide mouth’ design, but only the standard mouth fits the insulated silicone Sport Cap (£10), designed for taking generous sips on the go.
Key specs – Material: 18/8 stainless steel (dishwasher-safe); Capacity: 600ml; Size: 26.5 x 7.3 x 7.3cm; Weight: 295g; Colours available: 3 (more colours available from other retailers)
3. SIGG Hot and Cold ONE: Best cheap durable flask for hikers
Price when reviewed: £26 | Check price at Amazon
- Great for… Durability
- Not so great for… Lid feels less durable than body
Drop it, dent it, dishwash it, drink straight from it, even brew tea in it. This fab lightweight flask is designed to survive anything without messing with the temperature of its contents, keeping your brew comfortably hot for 12 hours.
The two-part locking lid doubles as a rotatable spout, so it’s ideal for taking a sip when you’re walking, although the plastic part of the lid does feel somewhat less durable than the metal. We also love the classic Sigg handle, which doubles as a lever so you can open it using a stick if your hands are cold or dirty. There’s even a built-in tea filter, so you can make tea using loose tea leaves or whatever you find on your adventures.
Key specs – Material: 18/8 stainless steel with polypropylene strainer (dishwasher-safe); Capacity: 500ml; Size: 25.5 x 6.9 x 6.9cm; Weight: 381g; Colours available: 3 (silver, white, black)
4. Thermos King Food Flask 470ml: Best food flask
Price when reviewed: £25 | Check price at John Lewis
- Great for… Hot or cold food
- Not so great for… Drink!
The King is back, and this time he’s full of lunch. Here, the Thermos’s insulated stainless steel lid doubles as a serving bowl, and comes with a full-size folding stainless steel spoon. Stews and soups stay very hot all day, while fruit and tubs of yoghurt stay cool all day – or fridge-cold if you include an ice pack in the flask. Ice cream won’t quite go the distance, but if you pack the flask with a handful of wrapped lollies straight from the fridge they’ll stay frozen for a few hours.
Key specs – Material: 18/8 stainless steel (not officially dishwasher-safe); Capacity: 470ml; Size: 14.2 x 9.4 x 9.4cm; Weight: 390g; Colours available: 2 (more colours available from other retailers)
5. SHO Food Flask 530ml: Best food flask for the style conscious
Price when reviewed: From £20 | Check price at Amazon
- Great for… The style-conscious
- Not so great for… Sheer insulating power
If you’re looking for a food flask that eschews the usual rugged look in favour of something a little more sleek and stylish, the SHO food flask is the option for you. It comes in a wide range of colours, ranging from pastel matte options to fun gradient styles, making it a perfect camping or travel accessory for the style-conscious among us.
A solid performer in testing, SHO’s food flask kept water chilled for the advertised 20 hours and even managed to keep a portion of ice cream very cold, albeit a little melted, for the same period of time. Similarly, it kept hot food such as pasta piping hot over a period of 10 hours. The flask’s design also proved practical as well as stylish, with neat touches including a handy foldable spork, which stores in its lid, and a rubber carry handle. While the 530ml version is suitable for single portions, those of you looking to share may want to opt for the more roomy 800ml option.
Key specs – Material: 18/8 stainless steel (not officially dishwasher-safe); Capacity: 530ml, 800ml; Size: 10 x 10 x 17cm; Weight: 480g; Colours available: 18
6. Contigo Autoseal Chill water bottle: Best flask for cold drinks
Price when reviewed: £25 | Check price at Amazon
- Great for… Keeping cold drinks cool in style
- Not so great for… Hot drinks
If you’re not a big hot drink fan but still want an exceptional flask to keep drinks cool on camping trips, long days and overnight stays, this slick offering from travel favourite Contigo is ideal. It claims to keep drinks cold for 28 hours and during our testing, it lived up to this. While the temperature will drop a tad when ice begins to melt, we found that iceless liquids were the same temperature 28 hours later as they were when first added. In some instances, they stayed chilly for far longer than the time stated too.
It’s 100% leak proof – no matter how hard we tried, we couldn’t get any liquid to escape and the automatic opening trigger means you can drink from it one-handed with ease. Finally, there’s an additional loop handle on top so it can easily be attached to bags or simply carried this way. All in all, this is a brilliantly stylish and robust alternative to a flask.
Key specs – Material: stainless steel (plastic lid dishwasher safe) Capacity: 720ml; Size: 7.6 x 7.6 x 27.4 cm; Weight: 382g; Colours available: 2
How to choose the best vacuum flask for you
Flasks have come a long way and today’s best vacuum flasks are mini engineering marvels. Made from multiple layers of BPA-free and rust-proof stainless steel, these flasks should survive years of bumps and knocks, keeping you in hot cuppas and ice-cold drinks season after season.
They also win big on green points, doing away with the need to buy drinks in single-use cups. If your flask is big enough for lunch you can save on both money and plastic.
How much should I spend?
You can buy flasks for next to nothing but, given how often you’re likely to use your flask, it’s worth spending a bit more for quality and durability.
You tend to get what you pay for when buying vacuum flasks. Of course, you can get flashy designer flasks, but if you’re looking for quality alone you won’t have to spend more than about £25-£30. That may seem extravagant for a drinks container, but you will soon save much more on drinks and lunches.
What features should I look out for?
18/8-grade steel: Today’s best flasks are made from stainless steel that doesn’t secrete chemicals (they’re BPA-free, in other words) or weird flavours. The best of the best are made from 18/8-grade steel (aka 304-grade), whose high nickel content makes it rust-proof and extremely durable. It’s also non-magnetic, which may disappoint if you would hoped to adorn your Thermos with fridge magnets.
Multi-wall insulation: Double-wall insulation creates a vacuumed layer, which is vital for keeping hot drinks hot and cold drinks cold. Some flasks include more layers for even better insulation. The 100% stainless steel construction of today’s flasks means there’s no risk of inner walls shattering when dropped.
Insulated cup: Good flasks also pay attention to the insulation of the detachable cup, if they have one. This is so your drink stays warm while you’re drinking it. Meanwhile, the outside stays cool, so you don’t risk burnt hands.
Capacity: Bigger capacity means more contents to enjoy. It also means more weight to carry, but only if you fill it to the brim. For best insulation, buy a flask that’s slightly bigger (but not heavier) than you need, and leave a couple of centimetres of air at the top. We’ve included capacity and weight info for all our flasks below.
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