When in doubt, turn to bodily fluids.

Another true-life inspiration. Not me, but a suitemate. Got so drunk on Halloween he threw up into his own hat, removed from his head only seconds before. As you might imagine, a mesh-backed baseball cap is not the most effective device for retaining large quantities of any kind of liquid, and it promptly spilled onto his "date." I don't think either of them remembered it the next day.