For what its worth, I've had gallon water bottles stored in a car overnight at temperatures as low as about 15F, and they did not freeze. If it did start to instantaneously freeze, there was usually enough water for a dehydrated breakfast pouch.

At least with the ones I have used, the bottles (either gallon or pint size) seem to freeze just fine. The indentation in the side of the gallon jugs pop out. The bottom of the pint size bottles seems to push out, rendering them unable to stand on their own.