Want to make an easy change for the planet? Cut your use of single-use plastic by investing in a good-quality insulated flask for hot and cold drinks alike.
These eight flasks are ideal for carrying your morning coffee and afternoon cuppa with you, or for refilling with water throughout the day.
Insulated flasks are a more practical choice than reusable coffee cups as they are leak-free and use a vacuum seal to keep drinks at the right temperature for hours on end, so you can keep hydrated throughout the day – and no more disposable coffee cups or plastic water bottles end up in landfill.
Flasks come in many shapes and sizes and at multiple price points, so think about when you’ll use yours before you buy one.
If you want a flask for family hikes, a big thermos with a cup-style cap is a good choice, while if you’re commuting, a lightweight flask that fits a cup of coffee and can be stashed in a backpack is a better shout. As a guide, 300-400ml is a good size for carrying coffee for one person.
A thermos with a handle is a good idea for drinking on the go or in the car, or if you have arthritis and need something easy to grip. Look for a cap that screws on tightly or pops closed, and we recommend picking a flask made without BPA, a chemical commonly found in food storage containers that can leach toxins.
Thermoses need regular cleaning with hot soapy water to avoid odours, and stainless steel ones tend to be the easiest to keep clean.
You can trust our independent reviews. We may earn commission from some of the retailers, but we never allow this to influence selections, which are formed from real-world testing and expert advice. This revenue helps to fund journalism across The Independent.
Blue Marble bamboo 360ml flask
Eco-friendly brand Blue Marble offers a great selection of flasks, but our favourite is this handsome, tactile bamboo and stainless steel number. Smart enough to give as a gift, beautifully made and a joy to use each day, it will keep drinks hot for eight hours and cold for 12. It even comes with two sizes of stainless steel strainers, so you can make fresh tea or fruit infusions on the go, and the whole flask is quickly and easy to clean.
Buy now £19.95, Amazon
Lifeventure thermal mug 300ml flask
The most pocket-friendly of our top-rated flasks, Lifeventure’s colourful and tactile flasks are cheap and cheerful but still do a good job of keeping coffee hot or water cold when you’re out and about all day, with a reliable screw-top lid to avoid spills even if the flask is being bounced about in a rucksack or bike pannier. Small and lightweight, it’s a great choice if space is at a premium, and we think it’s a steal at under £12.
Buy now £11.99, Lifeventure
Thermos King 1.2 litre flask
The big daddy of our roundup, the classic Thermos King’s stainless steel interior keeps both hot drinks hot and cold liquids cold for up to 24, with a lid that works as a large cup and a useful handle built into the side of the flask for easy carrying. This flask was one of the toughest flasks on test – if you need a flask for work or daily use in the outdoors, this is a hardy, long-lasting choice. Smaller sizes are available, including a useful 900ml size.
Buy now £24.99, Robert Dyas
Chilly’s 500ml flask
You’ve probably already spotted Chilly’s bright and beautiful bottles out and about – they come in myriad eye-catching prints, and Chilly’s often collaborate with artists and designers on limited-edition collections. These tall bottles offer substance as well as style, though, keeping hot drinks hot for up to 12 hours and cold drinks cold for 24, and we found them reliably leak-free on test. BPA-free and made with stainless steel, you can also customise or even engrave your own work of flask art on the Chilly’s website. The only difficult choice is choosing between flamingo or watermelon print.
Buy now £20.00, Chilly’s
Hydroflask wide mouth 355ml flas
This excellent flask is one of the most versatile we tested. It holds 355ml of liquid, ideal for your morning coffee, and is designed to pop under barista coffee machines and to fit into backpack bottle pockets. It keeps hot drinks hot for six hours and has a handy flip-up lid and wider mouth for easy drinking on the go – the perfect flask for the daily commute or for solo hiking trips. It’s BPA-free and there are two larger sizes available (plus a cute child-size version for small fans of hot chocolate).
Buy now £26.95, Hydroflask
Klean Kanteen TK Pro 750ml flask
It may be the priciest flask on test, but it’s one of the best-performing. Klean Kanteen reckon it keeps liquids hot for a whopping 28 hours and cold for up to 90, and we certainly found that this flask did an excellent job of insulating drinks from dawn till dusk. This smart thermos is plastic and BPA-free, with an easy to clean stainless steel interior and a streamlined design that makes it easy to pop into a backpack. The outer lid doubles as a deep cup, holding 305ml of liquid.
Buy now £39.95, lean Kanteen
Sigg hot and cold one 500ml flask
Hot and cold by name and by nature – this futuristic-looking thermos offers 12 hours of insulation for hot drinks and 20 for cold. The stainless steel interior is BPA-free, and we love the flask’s clever lid, which can be popped open and closed with one hand, ideal for fast-paced hiking or when you’re driving. The leak-proof lid also has an integrated handle, which can be clipped onto a backpack, and the slim design of this one means it fits easily into rucksack pockets and car cup holders.
Buy now £22.99, Amazon
Jack Wolfskin Thermo Bottle Grip 900ml flask
We like the black Batman-esque looks of this smart thermos, and that matte coating is also easy to grip on the go or during a rainy walk. A stainless steel interior does a good job of keeping drinks at their original temperature during the course of a day, and the lid doubles as a well-sized mug. It’s a simple but effective choice of flask that will hold coffee for three, although it is also one of the heavier thermoses we tested.
Buy now £24.00, Jack Wolfskin
The verdict: Insulated flasks
There’s a good choice of thermos in varied sizes on this list, but our favourites include the handsome Blue Marble bamboo flask for tea, the Hydroflask for coffee on your commute and the hefty Thermos King for work and family use.