I used to love vanilla cokes, both diet and ordinary, but you never see them any more. I haven't liked any of the zero versions of the coke drinks that I have tried yet. Dr.Pepper Zero I think was the most disgusting.
The one UK version soft drink that I absolutely adore, and drink WAY WAY too much of is Diet Cherry Coke, has to be diet, not ordinary. There is something in it that just does it for me. If that isn't available then It would have to be Cherry or ordinary coke, but the ones imported from eastern europe, not the UK ones. They have a different mixture I suspect because the non UK ones just use ordinary sugar, and the UK ones use destrose or some sugar-deriative chemical... or maybe its the other way round?? What I do know is the good coke is the one with arabic writing on it. and the good cherry coke is easy to spot because it has a black lid. They also say 0,5L instead of 500ml. Find them in your local corner shop, or when you are in central london Benjys!