Yeah, coke, pepsi, etc. These are all highly acidic and will eat the rust away. You can also save your flat pop bottles (2liters) and when you need to clean your toilet, dump the old flat pop in there and leave it for a couple hours (or the next time you gotta go) and viola...squeaky clean porcelain! LOL
Painting seems to just create a mess, if you ask me.
For cleaning your gear, dipping in coke may be hard to do depending if its a fixed loop, or something.