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Question

i've found recipes for making your own cream soda and root beer and they both ask you to ferment them using yeast(no they are not alcoholic drinks, its for carbonation). I wanted to know if there was any kind of substitute that can be used in place of the yeast or do you know what else can be used to carbonate them.

Answer 1

You can get a tank of CO2 and pump it into the drink under presure.  You used to be able to buy machines for it.