We take tervis cups (24 oz) for the adults and the kids usually take a smaller one (12oz or so). I will tell you that when we were on the Dream in August, they were asking people not to fill personal cups at the machine. A CM actually said something to my husband. They were very nice about it, but were very concerned about people filling cups they were drinking from and getting germs on the machines. We use tops so ours should have been fine. They just asked that you fill up one of the paper cups and dump into your own cup. Just something to know when you go.