Sodas are sold in quantity of 6, per the menu. Probably same as at a bar. Expect ~ $3 per can. The menu doesn’t show prices, so they don’t have to keep updating it.
I ate the snacks from the minibar on my MSC cruise (price list was in the room - and reasonably priced). Never have ordered them from Room Service on Disney. Might be the old saying, “If you have to ask, you can’t afford it.” I know better now, but often live by it. And I just walk to the soda station for drinks. It is never that far away.
You can pick up snacks and sodas at Preludes at show times outside the Walt Disney Theater. And then don’t have to wait for delivery when ready to munch. (I assume you don’t want to transport snacks in you luggage.).
Let’s see if anyone has actually ever ordered snacks and drinks...