Bah, no EXCUSE for over-priced coffee house or beverage stand prices for real
Cream Soda. Carbonated beverages really aren't too terribly difficult to make, as I've recently discovered. The biggest issue is storage. Here's one interpretation of Cream Soda.
Makes a whole lot (about 130 oz. or so)
Simmer 2 quarts of water, the cinnamon bark, the vanilla bean, the raisins, and the sugar for about twenty minutes.
Take it off the heat, and add the cream of tartar. This would also be a good time to add any syrups, oils, or essences you'd like (mint, wintergreen, strawberry, whatever).
Cover it, and let it cool for about half and hour. Strain the mix into a large glass jug (or a carboy), and add the remaining 2 quarts of cool water. Hydrate the yeast with the lukewarm water, then add it to the jug.
Bottle the soda, then store in a dark, temperature stable place, like the basement. Check it's carbonation after two days, and don't let it work for more than three. Refrigerate once it's good and fizzy.
When serving, put a dollop of fresh table cream at the bottom of a glass, then pour in the soda. I guess you could do the soda first, then the cream, but that'd just be crazy.