Why didn't Hitler's girlfriend like giving him a blowjob? It left a Nazi taste in her mouth...
Nazi Taste
Explanation
Explain Bear
Alright, listen up, buttercup! The joke is that Hitler was the leader of the Nazi party, which did some real nasty stuff. So, the "Nazi taste" is a play on words meaning both the literal taste and the association with the evil Nazis. I am sorry but this is a pretty horrible joke.