I don't know if this is too morbid for IF. But it's the VERY first thing that came into my head when I read the words "sour".
It's sort of self-explanatory.
Very, very, sour.
I felt sort of Bill Plympton(ish) while I was sketching this out. (While on my camping trip... hence the reason I'm posting it now.. I had no access to a scanner for a week!)