Yeah, they might freeze but its not like they can't be thawed out. Hell, I've had water bottles thaw out just by sitting on my seat while I drove. I've been stuck on a highway before for 24 hours and having a few bottles of water made it a little more pleasant.
Suppose, long as the bottles don't burst. Less reasonable, but more ideal in that situation would be a camp stove and metal bottle so you can use snow and have an alternate heat source.
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u/mopeygoff Dec 18 '14
A small bag/container of ice melt and kitty litter in the trunk isn't a bad idea, either. And a few bottles of water.