Is Any major brand Vodka (plain, unflavored) low FODMAP?

Yes — plain, unflavored vodka is low-FODMAP, no matter what it was distilled from. Vodka starts as a fermented mash of wheat, rye, corn, potatoes, or even grapes, but distillation carries over only alcohol, water, and volatile aromatics; the sugars and fructans in the base mash stay behind in the still. That is why a wheat vodka poses none of the fructan concerns wheat bread does. US rules do let producers round out plain vodka with up to 2 grams of sugar and 1 gram of citric acid per liter without declaring it, but that works out to well under a tenth of a gram of sugar in a 1.5 oz pour — nowhere near a fermentable load that matters. What changes the math are additions after the still: flavored and 'infused' vodkas can carry real sugar and fruit concentrates, and mixers like cranberry cocktail or orange juice are usually the actual FODMAP source in a vodka drink. One caveat that has nothing to do with FODMAPs: alcohol itself is a gut irritant and can speed up gut motility, so even a perfectly low-FODMAP pour can be felt by a sensitive gut. Keep the serve simple and the vodka itself is about as low as drinks get.

📏 A standard pour is 1.5 oz (44 ml). The mixer decides the drink: soda water with fresh lime keeps it low-FODMAP, while cranberry cocktail, orange juice, and flavored syrups are the usual FODMAP sources. Flavored or 'infused' vodkas are separate products — check those labels. Alcohol is a gut irritant on its own, so pacing still matters.