Well... you could just throw in a bunch of apple juice concentrate cans, or maybe enough to, if you'd mixed them with your 2.5 gallons of water, reconstitute 2.5 gallons of juice instead, then throw some extra juice on top. It'll be awful high ABV though, and a lot of people say that white sugar gives a pretty poor taste when its a primary fermentable. Still, at this point, all you have to lose is a few cans of concentrate and some extra juice. On the plus side, your yeast can most likely handle the high sugar concentrations. Give it a shot!