i-adjective
smelling of rotten food or drink
Describes the sour, stale odor of spoiled food or beverages. Rare and literary; in everyday speech, 腐った臭い or すっぱい臭い are more common.
台所からすえ臭いにおいがする。
There's a smell of rotten food coming from the kitchen.
古い酒がすえ臭くなっていた。
The old sake had gone off and smelled sour.
腐る is the common verb for 'to rot' or 'go bad', while すえ臭い specifically describes the resulting smell and is rare.
すっぱい means 'sour' in general, whereas すえ臭い implies a spoiled, unpleasant sourness.
Compound of すえ (饐え, spoilage) + 臭い (くさい, smelly). The exact origin of すえ is uncertain, but it is associated with food going bad.