Those Familiar with Second Cup

ThreePartBreath

I've look all over Google for an answer to this but to no prevail, so I've come to MFP in hopes that someone has got the information I'm looking for.

At Second Cup they serve Italian Sodas, and the one I frequent has an option for SF syrups.
Does anyone know what base they use? I've read that soda water (which has 0 calories, I guess?) is the norm., but I've also seen people say that Italian Sodas are made with regular Sprite.

I'd really like it to be soda water because then there's very few if any calories in a drink made with SF syrup.

Anyways, does anyone know? Should I just ask next time I go?
Thanks to whoever replies!