That's true, and I wasn't paying attention. I am frequently surprised about what the wait staff will bring when asked that is not on the menu.
A couple of cruises ago, a tablemate at dinner was asking a Filipino waiter about a specific local dish for breakfast. The waiter replied the crew has it frequently. When the tablemate said he wished he could try it the waiter said he would arrange for it, and the Filipino meal was specially prepared for the guest and served to him the next morning.
Ok, well I got way off topic for a juice post. I guess the moral of the story is that it doesn't hurt to ask for the juice you want, and if they tell you it costs extra you can reconsider.