To get maximum performance from your flask, you should always pre-warm it before use. Fill it with boiling water and leave to stand for five minutes or so before emptying and refilling with your chosen brew – such as tea, coffee, soup or hot chocolate. Filling your flask right to the top will also help minimise heat loss. Temperature Test: Method Key attributes: Very light, design enables one-handed drinking, wide mouth for easy filling and cleaning. When single-use plastics started getting a bad rap, S’well became the drinks bottle of choice for a host of celebrities and ‘influencers’. But they’re not all style over substance – the design consists of a triple-walled construction incorporating a copper layer for improved insulation. This flask is lightweight and practical – the ergonomic shape makes it easy to hold, the really wide mouth makes for easy drinking, filling and cleaning, and the grooved lid makes it easy to open, even if screwed on tightly. It’s sure to draw admiring glances if you leave it on your desk at the office. It’s just a shame that the capacity is a bit small, and it’s relatively expensive for a little flask. Full Specifications 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.

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 brilliantly stylish and robust We’ve reviewed a selection of the best thermos flasks, ranging in size from 470ml to a whopping 64oz (1.8 litres). Bigger flasks usually retain heat better than smaller flasks, but are typically bulkier and heavier. We’ve compared their performance with our own temperature test. What Is The Best Thermos Flask? Like almost any decent bit of outdoor kit, a good vacuum flask should also be robust and durable. All the flasks we tested are made of high-quality 18/8 food-grade stainless steel that resists dents, dings and scratches. The trade-off with steel flasks is that they can be heavy, although modern designs are shaving weight all the time, and in some cases, they now weigh little more than a standard plastic drinks bottle. Capacity: 500ml / Temperature test: 0 hrs 90°c, 90 mins 89.3°c, 4 hrs 82.8°c, 6 hrs 79.2°c, 8 hrs 75.3°c, 24 hrs 50.9°c / Stainless steel interior and exterior / Cool-touch, no-slip finish / Protective silicone rings for ultimate durability / Two part stopper for smooth pouring. BUY NOW: THERMOS.CO.UK Other useful design features to look for include a wide mouth, which makes for easier cleaning and filling (especially if you want to add ice cubes to your flask). In addition, many larger flasks incorporate ‘twist and pour’ spouts, so you can pour from the flask without having to completely remove the stopper. An integrated cup is also useful. Smaller flasks often feature lid designs that allow on-the-go swigging or one-handed operation.

We examined each flask and its pouring mechanism and attachments for faults. We penalised flasks that had faults affecting their usability.

EXTREMELY DURABLE: Our leak-proof thermos bottle has withstood speeding bullets, 4000 ft drops and category 5 hurricanes; The iconic style and rugged durability of this insulated bottle means it’s made to go anywhere

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. verifyErrors }}{{ message }}{{ /verifyErrors }}{{