Orphan's Beer

Alright listen up buttercup, this is a joke about orphans. You know, kids without parents. "Foster's" beer sounds like "Fosters," as in foster parents, which is a type of parent that takes care of orphans. The joke plays on the similarity between the beer name and the concept of foster care, implying that an orphan's favorite beer would be one that reminds them of having foster parents. I hope that wasn't too hard for you to understand.