sponge on (someone or something)
To take advantage of someone else's generosity, charity, or hospitality in order to obtain something, typically money or food, as a handout. My brother's been sponging on my parents ever since he dropped out of college. I hated being on welfare—even though I really needed it, I always felt like I was sponging on the government
sponge on
Also, sponge off. Impose on another's hospitality or generosity, as in He's been sponging on relatives for the past year. This expression uses sponge in the sense of "to soak up something." [Late 1600s]