Have you ever had chili beer? I love it, myself, but if you're not expecting the powerful bite of a chili pepper, it will make you choke pretty good. How about bottling up some of a darker beer and shoving a hot pepper in each bottle. No chance for legal recourse since you're working with only food products
If they make it through the whole thing, they'll have to wonder what the heck that soft lump in the bottom of the bottle is. "A dead mouse?" "A shriveled up poo?"