a large, cheesy grin on a person, similar to the one the Kool-Aid man has in the commercial. A Kool-Aid Smile is usually seen when a person has accomplished a major feat or task, or something extraordinarily good happens to that person.
Ryan walked out of her house with a big ass Kool-Aid smile on his face.
When you have a stain around your lips like you just drank a glass of Kool-Aid. Or her lip stick on the skin surrounding her lips. Or her filter isn’t lining up with her lips giving her the appearance she just drank a glass of Kool-Aid.
When the filter don’t cover your lips right, it looks like you got a Kool-Aid Smile.