As many people have mentioned, you can boil water in one of these stainless bottles. Of course a dedicated pot or canteen cup works better for cooking or purifying water. Here is something that has not been brought up though. Every time I go backpacking and it drops below freezing, I am having to sleep with my water bottles in my sleeping bag to try to keep them from freezing. In one of these stainless bottles, if it does accidentally freeze, you can place it on top of a stove or fire to melt the ice inside the bottle. You can't do that with a polycarbonate bottle...