Soda. In this instance I used cherry Dr Pepper.
Agar-agar powder. I found some at an Asian supermarket, although I have also seen some at heath food stores. It works in a similar manner to gelatin, but it is a plant product rather than an animal one.
Small or medium pan
muffin tin (or whatever tray you have and like that can handle hot liquids)
First, figure out how much soda and agar-agar you will use. I used a ratio of 1/2 teaspoon powder to 1 cup soda. Using less made it not quite solid.
Heat the soda under low heat. Once you see bubbles the size of tiny peas that are not from the carbonation, stir in the agar-agar and let it continue to bubble for 3 minutes. Depending on the soda you use, a wooden spoon might be temporarily stained, but so far the sodas I have tried have washed out.
Pour the liquid into the muffin tin, and once it has cooled off a bit, refrigerate for at least half an hour.
Once the soda is gelled, slip it out of the muffin tin. Knives and spatulas work pretty well for leaving the shape intact. You can put a bit of whipped cream on top, spread it on toast, or as it is with a spoon.
***Important! This is still a work in progress! ***
So far, the gelled soda tastes mild compared to the actual soda. I came up with the type of soda, ingredient amounts, and times by just trying things out, and I will continue to experiment. If I find ways to make the recipe better, I will update the Instructable. Thanks for reading!