Dextrose is the best. It is basically sugar, but much cheaper. Check www.bulknutrition.com
Acid in grape juice do more harm than good? LOL Think about it... Your stomach contains HCL(hydrachloric acid) and that can eat through iron. The acid in grapejuice is not going to harm a thing.
If you dont want to buy dextrose, I recommend using grape juice(concord) and ALA(alpha lipoic acid). You can also fint that at bulk nutrition