Water in a Polycarbonate plastic bottle and placed in my freezer worked for a while. But repeated use of this caused the bottle to burst, even though it was not filled up to the top. My guess is that polycarbonate was not designed to expand and contract like this. At today's bike shop, they offer the soft plastic bottles and the polycarbonate type. The soft plastic has a distinct odor to it and one has to wonder if its good for you.