I believe the IG style sway prefers one or the other for a girl sway, but don't remember which or why exactly. Something is telling me it may be ion related and if it was, rest assured that ions have been debunked for swaying.
I drank the stuff out of the tap during my pink sway and it was fine for me. I can't imagine that the brand of water would sway all that much one way or another. Personally I wouldn't worry about that for my sway. If you want to have beverages that help to sway a bit, stick with something a bit more proven like a diet soda with aspartame or crystal light. Hope that helps.