To Keep Water from Freezing
Outdoor activities require you to drink plenty of water. The problem with water at 20 below zero, of course, is keeping it in a liquid state. Even an insulated water bottle or other insulated container will freeze up before long.
The trick is to use either your body heat or the warmth of the earth. While out traveling, a water bottle tucked inside your coat will stayed thawed. At night I always keep a small tightly sealed water bottle with me in my sleeping bag. Filling it with warm or hot water isn’t necessary, but doing so warms your bag up very nicely. Around camp, find a spot under deep snow where the ground is not frozen, dig out a stash hole, and keep water and fresh food items there. Cover with grass or cloth, then with a thick insulating layer of snow and your items are safe through the harshest of winter nights.
In the winter, stick with non-alcoholic fluids, such as water. Alcohol dehydrates you (you dump it in your gas tank to eliminate moisture), and gives you a false sense of warmth. It should be used with great caution in extreme weather, especially if you are staying out overnight.