These bottles would be a nice little addition to office buildings and a good find when you do come across one, but I think game balance would be better if they were fairly uncommon as many could have already been taken by survivors. Also, they should not fit in a backpack. Instead, they could be implemented as their own carrying device that can only contain liquid. However, one question that may need to be decided is what happens when you add different liquids to the bottle such milk, water, alcohol, soda, etc...