If you are talking about night hiking, you blow back the water in the hose to reservoir and keep the bite valve near body to keep ice from forming. You should consider a 1-liter Nalgene bottle in a insulated sleeve, in severe conditions. The insulation sleeve for the tube is just above useless in the 20s.
If you are talking in camp at night, just empty it. I don't like putting these thing in my down sleeping bag.
