1. Shut up about San Pellegrino. It's just the new Schloer or whatever that stuff is called. Also no one wants to hear about the detox thing at Itsu.
2. Additionally, nothing that costs more than 70p for a can (non-railway-cafe prices).
3. I will accept own-brand supermarket stuff (not m&s) if you allege that it's better than the bigger brand stuff.
Anyway. With that in mind:
The answer is Pepsi Max OR Fanta Twist.