Boylan Bottleworks creates a range of diet sodas that can be found at health food stores. At 11.6oz per bottle, they have 0g carbs and are Splenda flavored.
Splenda is pretty much a perfect sweetener, with no off flavors at all. It tastes just like sugar. So it's no surprise that the diet cream we tasted was extremely good. Everyone I've had try this has loved it.
Boylan also makes a diet root beer, diet black cherry, diet cane soda, and diet birch beer. These are often not flavors you can find anywhere else!
It might be hard to find these in your local area. I did find a website that carries them -
This website list the bottles at $1.45 for each 11.6oz bottle. There is also the hassle of shipping and waiting for them to arrive. So you have both a higher than normal cost and an inconvenience issue
I suppose some soda vending machines now sell sodas at $1.50 each, so the price shown depends on your definition of high. These sodas are definitely very tasty, so it might be worth it to you!