Per rccl website:
The fountain soda package entitles you to unlimited refills at any of our bars or lounges, Windjammer Café, Main Dining Room and our private destinations. A complimentary Coca-Cola® souvenir cup is included as part of every fountain soda package. The cost of a fountain soda package is determined by the length of your stay, with an average daily cost of $6.50 for adults and $4.50 for children* plus gratuity. (*Child prices available for kids under 18.) The fountain soda package is sold for the entire length of the cruise vacation only. Only fountain soda is offered with the soda packages. The mini bar sodas are not included in the package and carry a separate charge.
Enjoy savings off the onboard price by pre-purchasing online.