There have been a lot of articles expressing concern about carcinogens when you freeze water bottles, so to keep my water bottles cold, I bought a soft-sided thermal cooler. I take the old used water bottles and fill them halfway and freeze. I put an indelible marker on the cap (these are not for drinking), but I put them in the cooler with the fresh water bottles, and you have cool water all the time -- even on very hot days, but you don't have melted ice inside the cooler.
