Drunk, Obnoxious – This is a common sight at almost any social event that lasts several hours and the drinks are flowing readily. This person, who may or may not be an ass when sober, becomes one when imbibing past their limit. At this point this person is a drag on the party, or at least his immediate area. This person is one that you will want to watch. They have potential for property damage and carnage, especially if they get behind the wheel.
What else you might try – Make sure this person has a ride home, and encourage him or her to depart under assistance, if possible. Unfortunately, coffee will only make him more wide awake. Food will help a little, but time is the only cure, which will hopefully he will have been long taken away from your event.