The problem here is that the iPhone still has (or, had) current running through it. It's probably toast.
The only way to give it a thorough cleaning is to take it apart, desolder the battery, wash the individual circuit boards in distilled water, let them dry thoroughly, reassemble and pray.
But my guess is that your friend's efforts would be better spent taking the phone to an Apple store, explaining the situation truthfully, and seeing what happens. Either the store manager will take pity on you and you may strike it lucky with a replacement, or you might get charged the flat repair fee ($249 before the price drop, it may be less now). Even so, $249 isn't bad for getting a like-new iPhone in excahnge for a beer-soaked one. 🙂