Nalgene Wide Mouth 1 L
1 L, wide mouth, boiling-water safe
Fill it with boiling water at dinner and it is a hot water bottle all night, then drinking water in the morning — that second job is why we recommend hard plastic over any soft flask above 4,000 m.
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Do not buy this if: Nobody on a cold trek. The hot-water-bottle trick alone justifies it.
Not every route needs it. These are the ones where our guides would put it on your list.
Everything else we recommend in bottles & bladders, including the ones we think suit a different trekker.
Best insulatedHydro Flask Wide Mouth Insulated
On a −15 °C morning an insulated bottle is the difference between drinking and chipping ice; the weight penalty is real, and one of these plus a Nalgene is 700 g of bottles.
