Back on prohibition days “I am told by old timers” The sold a thing in markets called “Welch’s Bar”
It was basically yeast and sugar in a cake bar.
You just tossed it into the grape juice and voila!
My Dad was an Oklahoma native, which was a dry state until 1958. Folks went to Texas for their hootch or bought the local white lightning & flavored it with an additive called “Texas Noodle Soup” which made it taste sorta like whiskey.
BTW, stocking up on pints of Popov for barter sounds like a great idea.