They are $5 per day and meant for just one cruise. However, people do bring them back on repeat cruises. They are ship specific - so they can't be used on both ships.
Just got off the 7 day Eastern Magic. Bought the mug for soda. $39 for the 7 days. DW did this thinking that we had to pay for coke at lunch and dinner. Other cruise lines charge for coke at meals. Also the topsiders buffet did not have Coke available to drink. I personally do not think it is a bargain. You would have to fill up between 3 and 4 times a day to get your money back. Since the only time we really wanted a coke was at a meal, we chose poorly and got the mug. On the other hand, I do use the mug now for coffee on my way into work each day!!!
In the dining rooms, sodas are free. At topsiders (Beach Blanket on the Wonder) they have fruit punch, iced tea, and coffee and I think milk. At the drink station they have fruit punch, lemonade, coffee, milk and I think iced tea.
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