Interesting question. I'm assuming he's got an Avenger on standby with a bucket of rice or it's waiting in the quinjet just in case. But he usually finds a way to make his technology water proof so it's probably never necessary.

No. I am sure he has built a armor to withstand getting wet and going underwater or he could have made it Waterproof

Yeah but it get in all his ports and he couldnt charge the suit

His environmental exosuits can withstand a vacuum and extreme water pressure, everything down to monomolecular mist. He'll be alright with a little water.

No, rice wouldn't fix a wet Iron Man.

If you drop a laptop in a puddle, a big bag of rice isn't going to fix that, either.