I too was looking all over the internet on how to make the thc soda too. They have keep it such a secret. Since glycerol is sweet it seems like the candidate to add to soda since alcohol and any fats would not work. I was reading the book Wild fermentation by Katz. He had a recipe for Ginger beer (ale) non alcoholic. Extrapolating I made ginger rose soda and other sodas. I'll bet, though I dont know for certain the dosing, that adding the glycerin extract to the soda mixture would make the thc soda and you could make it with a variety of flavors. I used rose water with a little pomegrante juice coloring. You boil about 2 quarts of water with 1 1/2 cups of sugar, let it cool, add your flavoring and coloring, then add a little yeast (I used moncharat wine yeast sp) as well as your glycerin extract, place in the metal wire stoppered bottles that european sodas come in and in two weeks you have carbonated soda. It would need some experimentation but you dont need the expense of a soda stream.