First of all this is a great idea and I think I really needed a soda which is not sweetened in any way but still tastes amazing.
As far as the product, I love the peach and orange flavour. I found the cranberry flavour to be a little light, I personally would like the cranberry taste to be a bit more rich.
On the fizz, this is the area I really wish the product could be more fizzy. In addition I have noticed that if I don't consume it in one go the fizz is completely over in a few hours.
On the price, Personally I feel it is a bit expensive at Rs. 60 as compared to the widely available sugared alternative, which makes it a bit more difficult to consume it everyday for me.
Wish the best of luck to you guys though and hope you make it!