Very bad funky hot stale breath. Like morning breath. Humans and animals can have mouth ovens. Exhaling and others can smell your bad breath or for that matter the offending critter with funky breath odors.
He gave his girlfriend a mouth oven in the morning because he didn't brush his teeth, ate a tuna melt with garlic and drank a glass of milk. Contributing to his mouth oven was the fact he ate out his girlfriend the night before after he consumed that tuna melt with garlic, that glass of milk and after eating her out without brushing his teeth.