Spindrift from Costco... It's canned carbonated water with fresh fruit juice... No sweetener... But I make simple syrup and keep it in the fridge...
I was skeptical, but basically after sweetening, the grapefruit one becomes really good squirt, and the lemon one turns into really good seven up like they make at the Mexico factories... Sounds ridiculous, but it's so much lighter and more refreshing than soda... I'm a fan...