Adding to Nick's answer, I would give any and ALL players that continue to splash the pot a warning and the next time I would call the floor and explain that this player(s) continues to splash the pot making bet amounts difficult to confirm. Let the floor make a decision, perhaps this person should be asked to take a vacation for the rest of the day or week. However, that is up to the floor, not the dealer. If in your "small games", you don't have a "floor", then you as the event organizer need to decide whether your event needs this person.
In a cash game, there aren't any 'penalties' as there are in tournaments. If you can't get this person to change their behavior, then you have a difficult decision to make.