There are two types of cranberry juice - "100% cranberry juice" and "cranberry juice cocktail." I would advise against using the 100% cranberry juice. This recipe tastes best with cranberry juice cocktail, which is sweetened. If you do want to use 100% cranberry juice, you will want to add a little bit of simple syrup to help balance the flavors of the cocktail. Otherwise, you'll likely find the cocktail too tart.