WOW! why dont you burn him at the stake while he's down! he asked a simple question and you jump all over him!
500cc is way too much, in answer to your question, yes transmission fluid is a good assistance for an engine, it gets rid of carbon and free's off any crap sticking behind the piston rings, cleans intake valves and exhaust too.
As for water! not good in the tank, but CAN BE USED as a injection into the intake to break off carbon real quick, NOT a bucket full! its an old trick from years ago, mainly used on the intake nipple and a tube coming off it into a glass of water, then pinch the tube and with engine running and hot release/hold at frequent times the tube this will in effect break off any carbon thats flakey.
Same method as TRANSMISSION FLUID, Seafoam, injection cleaner, GM top engine cleaner, GM choke cleaner, carb cleaner.
So, to the ones that jumped all over his case, get your facts right before kicking him while he's down.
In answer to your question sir, yes, transmission fluid is good, but not 500cc, a few cap fulls should be quite sufficent.