It's no secret that soda cans are some of the filthiest things out there. They're kept in storage units where anything (from rats to insects) can leave their feces on them. Do you take that into consideration or do you just let your immune system take care of it for you?
Stomach acid is a powerful thing. Out of habit I'll use my shirt to wipe off the can but that doesn't do anything. I'd never wash it unless I see visible dirt on it.