water weights

I've heard before that if you don't have weights you can substitue a can of soup etc... to do exercises with. Sunday night we went to Sarahs for girl's night. I was carying 2 1liter cokes. As I was walking I swung my arms up and jokingly said something about lifting weights. It gave me an idea. Today when I was shopping I picked up 2 1liter bottles of water. They're cheap. It's not something I'll drink so no big deal. After I ate dinner tonight I took the bottles in my room and proceeded to "lift weights" doing exercises to strengthen shoulders and arms. It was quite a workout. Altough as I was doing this I noticed I had picked up the carbonated water. I might need to empty it out and fill it with regular water. There is a gym on campus but I heard it isn't all that good and a lot of the equipment is broken.