As long as it's not flavoured like the canned Heinz macaroni and cheese they have in the UK.

I'm just imagining cheese flavoured soda, and I don't think it would be that bad... if you used the right cheese. Sharp cheddar (the cheese flavour I associate with Kraft Dinner, though it's probably a blend) and carbonated water doesn't sound good to me. I'd sip it if I could (bariatric, I can't). Flat, I feel like the point would be lost. Might as well be hot dog water at that point.