Both, actually.

The cooler holds four .7 liter bottles very nicely, and they are part of my general preparedness plan. I want to find out what they go through, and how often I need to change them out.

There are also 2 1L bottles in my GHB in the trunk, plus a couple of food bars. This will tell me what those are going through, too.

I also just enjoy doing this sort of thing. The classes with labs were always my favorites.