Can only think of a loophole with negative consequences. Korsakoff’s Syndrome, an amnesiac syndrome where people can’t remember beyond a short time period, a la “50 First Dates” - they forget anything they’ve learned within the last few minutes, is caused by B-1 vitamin deficiency, most often via severe alcohol abuse, which robs you of B-1. Fortifying booze with Vitamin B-1 would eliminate the main cause of this syndrome. According to US regulations, vitamins cannot be added to food without labeling the food as such. But other US regulations forbid labeling alcohol with anything that implies that it might be good for you. So there’s no way to add Vitamin B-1 to booze in the U.S.