This is used in context of "he wouldn't bust a grape" as in he won't do shit. It's like saying someone wouldn't harm a fly as opposed to busting a cap, the sucka wouldn't bust a grape. Get it right youngsters.
That fool was talking about busting caps but he won't bust a grape!
Activities that depart from a person's normal (sober) behavior that take place after consuming an overabundance of wine.
Party Goer: "Wow, what's Marshall doing over there by the DJ? Is he disco dancing....poorly like he's in some weird time warp from the 70's?"
Designated Driver: "Looks like he's been Fueled by the Grape again"
Party Goer: "Cool."