One company that I cannot remember marketed their creatine using the dosages of glucose that are used when people are given glucose (blood sugar) tolerance tests or insulin level tests. It makes sense IF the belief is correct in that the secretion of insulin and subsequent uptake of the glucose has any influence on the uptake of the creatine. In the US medical system, this test is administered using 75g.
So, anything with 75g or so of simple sugars in it "should" be effective if this theory holds water. Grape juice sounds great to me. I take mine with Hi-C.