to freeload for food

(coll.) to use sb else's Internet connection (with or without permission)

(coll.) to sit in on a class

(literary) to encounter setbacks; to have bad luck

(coll.) to ride in sb else's car to save money; to ride on a train or bus without buying a ticket (fare-dodging)

(coll.) to mooch a meal

(coll.) (often derog.) to piggyback on (sb's) popularity; to exploit (sb's) popularity to attract attention to oneself

to cadge a meal