Okay, so I tried the Coke experiment (because I'm bored), and confirmed this fact.

However, I dicovered on other interesting thing. I actually placed a can of Coke and a can of Diet Coke in the sink and filled it up. Initially, they both floated, but when I pushed them down into the water, the Coke sank and the Diet Coke came back up.

Upon further investigation, I found that the Coke would float until I filled up the area created by the upper lip of the can with water.

Now, I don't know if that's a weight issue or a surface tension issue, but it's interesting nonetheless. Well, at least as interesting as this topic is to begin with.