"Vodka works to some degree, but may have unintended consequences. :-)"<br><br>That was my first thought. <br>If you are willing to experiment, why not try this. Dont fight the freezing weather. Allow the bottle to freeze. Water expands one tenth its volume when it freezes. Do a rough calculation on how much water can freeze in a container without rupturing it. Then freeze it in your kitchen freezer. <br><br>I believe that I will try that with a 2 liter Coca-Cola bottle. This particular bottle says that it contained 67.7 fluid ounces. I imagine that if I fill it and then remove one cup (8 ounces) I will be well into the range of what it can handle without rupturing. <br><br>If you are wondering why I am working in ounces....well, I dont have any metric measuring cups.