Sierra Mist, Mountain Dew and 7 Up are all lemon-lime flavored carbonated drinks.
Since the first is only available in America, (PepsiCo owns the rights to 7 Up outisde the US) I drink Mountain Dew. I think it has been around 6-7 years since I've had Sierra Mist.
Sierra Mist most definitely. No wait, Mountain Dew! Actually, I'm torn between the two. Mountain Dew has that can't-beat taste and fizz, while Sierra Mist is lighter, but no less can't-beat when it comes to fizz. I'd actually choose Sierra Mist if I really had to pick between the two.