There are lots of things that can ruin your appetite, but from a kid’s perspective, there’s nothing more disgusting than your parents kissing. Dad’s clearly picked up on that and thinks his little note is quite funny. We’d be interested to see whether he succeeded in ruining his kids’ appetites–maybe they finally took a break from the junk food!
On the other hand, maybe the child just tossed the note aside and ate the junk food anyway. We’re pretty sure that any dad who writes a note like this makes “dad jokes” on a regular basis, so there’s a good chance his kids aren’t fazed by it anymore.