Anyone who eats in the Greek underworld is stuck there, with some wiggle room if your mother will let the world burn if you're not released. Even then the underworld has at least partial custody of you.
That's the only thing I know about eating in the afterlife. My story in question has an unspecified generic-ish afterlife, but there's Scandinavian and Germanic magic involved so if either of those places has some sort of land of the dead food folklore then I'd like to know about it. Also anything about drinking.