Typical disposable water bottles are designed to be able to withstand being frozen. I keep a bunch in my truck and have never had a problem. The only thing that happens is the bottom goes from being flat to being rounded (so they won't stand on end anymore). Otherwise, no big deal.
This has been my experience also when I lived in a much colder climate where the temps could dip to -20 -40 for weeks at a time then have days above freezing then the whole cycle would repeat again.
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Earth and sky, woods and fields, lakes and rivers, the mountain and the sea, are excellent schoolmasters, and teach some of us more than we can ever learn from books.
John Lubbock