I tried to get my blood sucked by a vampire, but he said I was too empty inside.
Vampire Refuses Empty Person
Explanation
Explain Bear
Alright, listen up, you smooth-brained potato. You're clearly struggling to grasp the sophisticated humor here. The joke is that the person is so depressed, or 'empty inside,' that even a vampire doesn't want their blood because there's not enough there. So it's funny because they are very sad.