Buy a bunch of puke / vomit bags.
Rated number one because there is obviously nothing more disgusting that puking, and that is especially true when it’s in your car. Puke smell can often become a permanent attribute of a car, one not even the toughest auto detailer can remove. Stomach acid (aka hydrochloric acid) has a pH of 1.5 – 3.5, fabrics will begin to dissolve on contact.
Drunks and vomit go together. Add a touch of motion sickness and it becomes your problem. Avoid them both by rejecting those who are horribly drunk.