I'm not familiar with the word 'zappy' but zap, zapped and zapping, are used in reference to a move or strike with sudden speed and force. They are exclamations used to express a sudden, swift action. I would guess that 'zappy' is used when referring to something lively or energetic, for example 'that's a very zappy song'.

"Sappy" means, overly sentimental or melodramatic. In a bad way.

That has to be one of the most obscure things a person could possibly ask. Have you, by any chance, been reading comic books or watching Saturday morning cartoons? (If they're still even around. The cartoons, that is).

Could you mean 'sappy'?

This is not a standard English word. It could describe a tune that is upbeat and lively.