NO. Don't listen to the people who say you can. Hamsters are EXTREMELY scared of dampness and water, trust me I've had many hamsters, and I know almost everything there is to know. DO NOT DO IT. Get a chinchilla dust bath.
Well bathing a hamster is not safe! Because if you bring him/ her out of the water it can get chills and get sick and you don't want this. It's not good if your hamster gets sick! Use pet wipes or go to your local petstore they may have something there to clean them
If he pees on himself then yes. He might start to smell like pee if you don't. But you have to be careful. You might drown him so be careful how much water you use and do not use shampoo, conditioner, hand soap, etc. He is a tiny little thing and can get hurt by what people put in shampoo & soap these days. Use pet shampoo instead. I'm not a hamster expert btw, I've had no experience! Lol!