Fruit juice, in particular, is not required. However, drinking a carbohydrate-rich beverage triggers insulin release, which helps better deliver creatine (as well as other nutrients) to your cells. Just be sure the carbohydrate content of your drink is of high quality, rather than simplified sugar sources, such as high fructose corn syrup. Refined sugars like these are concentrated, and can excessively elevate blood sugar levels and insulin. It is also best that the juice itself is non-concentrated, for the same reasons.
Regarding the amount, whichever carbohydrate-rich beverage you choose, one glassful should be adequate as you take CRUSCH. After that, ordinary water is best.