Use 'in the soup' when talking about problems or troublesome situations. He was in the soup after forgetting his wedding anniversary.
Pro Tip 2/3
Informal Tone
'In the soup' is casual language, not for formal situations like business or official documents. Don’t say 'in the soup' during a formal presentation.
Pro Tip 3/3
Figurative Expression
It's an idiom, meaning you shouldn't take 'soup' literally. It's a metaphor for trouble. Saying 'she’s in the soup' doesn’t mean she's in a bowl of broth.