that just creates 2 additional unnecessary steps. First, adding the money, and then getting the leftover balance back.
Just add a credit card to your folio and the drinks will get charged to it. Easy.
It's the same bill, but in the first case you are prepaying it and then trying to get the money back. In the latter case, your credit card gets billed automatically at the end of the cruise.
You will check your folio for any wrong charges daily in any case.