At night was not a problem. I dipped two 1 l. aquafina water bottles from stream (less than 35 degrees) treated with micropur tablet (other guys pump froze) and put next to fire for infrared heating and placed in sleeping bag. Good the next morning. Refilled from stream treated and then hit trail @ 9 with bottle inside my windbreaker and the other zipped in side pocket--temps below 10 degrees. By noon serious ice formation on inside bottle, by 3, slushy rock ice.

Inside pack not an option for I need to drink water during hike. I am already carrying 30# skin out, so I am not adding steel thermos bottles. (I was the kid who licked monkey bars during winter so I don’t do metal in winter anymore.)

I knocked any bladder due to hoes freezing. I don’t like to cook snow as it is waste of fuel (using alky stove, don't have pocket rocket) and time especially for liter every 4 hours when stream is on the away. Staying in camp was worst possible situation since we had limited wood, food, fuel and had it keep moving to stay warm and make way points.

So far, I like the Gatorade idea cause I need the sugar/salts which means I get three uses for item. Liked the hand warmer idea but I think the large thermal mass of very cold water would suck the heat down flat. The cozy idea is most practical and doable, not much weight gain but single use item. Vodka, well at least I get two uses if i put olive in bottle too.