Vinegar and battered chicken?
Adding vinegar 'to the chicken' might give it a slight tanginess, but its certainly going to cause issues with the  batter adhesion.  Sounds like a bad recipe (especially if your batter was just flour and water too!).

Every time I've seen vinegar in batter dipped chicken, its because there's also baking soda and it helps produce a lighter, airier batter.  And you put it in the batter, not on the chicken.