Hiking and playing with fire both have some risks too. Since it's a beverage can it can't be anything too toxic, but if it is lined with something, you may want to take steel wool and get that lining out. You'll eventually consume it otherwise.
Scott, I believe that even if the can has water in it, the part above the water gets hotter since the heat cannot be transferred to the water. I'd worry more about a lining peeling off there than in the water if this is the case.