My family of four, shared a mug. My husband cannot have caffeine, though, so his use was very limited. It was mostly just my 5 Y.O. and myself. We did pour the soda out into another cup, and then went back. No one said anything. we didn't make a production out of it. I think it would be rude to stand at the machine, and pour it into different cups. We went back to our lounge chairs.
Quite frankly, I thought it more of a pain, to buy the mug. We were at Coronado Springs, far away from the food court. Close to the pool, but it often closed too early to use when we got back. the only times we used it was our afternoon breaks. I didn't feel we got our $$ worth.
This trip, I plan on buying soda, at the grocery, and keeping it in a cooler. We drink more water when its hot, anyway.