chocolate is good in small quantities for all rats and ONLY female mice. For some weird reason male mice cannot eact chocolate (found that out the hard way... thanks mom...) Anyway, human foods are fine for them in small quanitites, but resist from feeding them things like burger king and mcdonalds. Don't feed them spinach because it can cause some vitamin binding, especially in pregnant females, and nuts and berries is always a great choice. Just like a dog, you cannot feed them too much of a good thing, it can cause fatty liver damage, resperatory issues, and lower their immune system. But, that's for those extremist rodent lovers who want to be on 'America's Fattest Rat!' And no, Al Capone doesn't count.
Tap water is fiiiiine. I lived in NJ and i gave my rats tap water... It took a while to get used to the third eye but i got used to it eventually.