Wear it under your jacket. Right on top of your base layer works best. Put insulation foam on the hose and blow back after drinking to minimize water on the hose. And also fill it with warm water.

If you want to wear it outside of the jacket, it will freeze. Blowing water out of the hose, wrapping the hose in insulation etc... helps, but it will still freeze. Even won under the jacket it may freeze, but it will take longer.