For MTB, Snowshoe, etc. in cold I use Camelback in insulated pouch, with insulated hose cover, insulated mouth piece cover.

If it's really cold I'll fill it with warm water.

If it's really, really cold, add a chemical hand warmer pouch to the insulated pouch.

Most important, after you drink, blow the hose empty back to the bag. That mouth piece is most vulnerable, and once if freezes it's very hard to correct in the field.