There is plenty to drink. The ship has different juices and there drinks without alcohol. The juices are an additional fee unless you get it in the dining room or order it through room service in the mornings.
Whatever you do, do not purchase the soda package because it does not include juices. In addition you could get Ice Tea fountain drinks from the dining room on the upper level, however be prepared to put alot of sugar. That's no charge.
Enjoy your trip.