Re: iced something or something on the rocks?
We use "on the rocks" for alcoholic drinks. If you said "Coke on the rocks" it would sound like you were trying to be clever.
Yes, Coke is countable the way coffee or tea or water is countable to mean a can/cup/glass of Coke, coffee, or tea.
Two Cokes and coffee please. -- Something you might say to the waiter.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.