Hot Soup is a variation of a Hot Lunch which, in this case, rather than delivering a solid log of crap, you deliver the liquified, diarrhea version thereof. It's heinous, it's awful, you can dazzle your friends by throwing its use out in conversation.
"Did you ever give your girlfriend a hot lunch?"
"No, but I wasn't feeling too well and gave her some hot soup to make myself feel better. Hot soup makes everyone feel better."