Carnival offers soft drinks cards for both kids (approx. $20.00) and adults ($30.00). On the Sensation two years ago purchased the kids soda cards -- adults were not available, but have since learned that most Carnaival ships now offer adult cards. These are good for sodas only and for use in the various bars and restaurants.
We are going on the Fascination on October 1. I booked the cruise directly through Carnival and at the time I asked about the soda card for adults. Since this is a 4 night cruise, I was told that the cost was $11.99 and could be purchased at any bar. It does include unlimited soft drinks.
We purchased a card for my husband (I dont drink sodas) and one for my daughter. I'd say my husband's card wasnt worth it...we paid more money for drinks in the long run. I still say we got screwed on my daughters card as well, but she ordered more sodas then he did, so it may have been worth it.
Drinks are only served in a glass w/ice. So if you order a drink in the lounges (like to see a show) expect it to be watered down by the time you get it. If you order it from a bar it is ok. If you order a drink not using the card you get a 20 oz bottle w/a glass and ice, but I think its $2.00 a bottle. You cannot use the card on room service.
FYI: Food or drinks are not allowed in Camp Carnival areas.