In Britain, “sherbet” is a word for a fizzy sweet or sweet powder. However, inviting someone to go to the pub for a few sherbets is not an invitation to eat sweets, but an invitation to drink a few beers. It is possible that this comes from the fizzy, frothy top on beers.

“Do you fancy a few sherbets after work tonight?”

Asking someone if they “fancy” something is a way of asking if they would like it.