If you want a cheap and effective way to inject co2, this is the ticket. The baking soda and vinegar
works but yeast is muuuch better. The reason is because yeast is actually a living organism
; when it's placed in water with sugar present, it becomes anaerobic and feeds off the glucose in the sugar for energy. After consuming the sugar, it releases co2 and heat as a byproduct.
The actual lifespan of yeast is like 30 to 60 days or something like that.. but this method is really only good for a week or two tops before you should bring in a new population of yeast, and fresh sugar. For best results, buy some sort of "rapid rise" yeast as this typically contains an enzyme to increase production dramatically (check the ingredients). Hope this helped the skeptic believers