The “Beer Kir” at Marco Moreira’s 15 East is a Japanese beer-based mixed drink: Sapporo is floated on a shot of honeyed sweet potato vinegar, adding a sweet-sour edge to the dry lager. For the purposes of home experimentation, we found Benímosu ($11.35 for 4 oz.), the same artisanal vinegar used in Beer Kir at Katagiri, a Japanese food store on 59th Street. Made in Kyoto from purple potatoes and koji rice, Benímosu has clean, rounded flavor that’s meant to be added to beer in a 1:5 ratio, which means a 4 ounce bottle of the stuff won’t even last a 6 pack. For more budget beer-vinegar drinks, Katagiri has a whole shelf of (mostly) fruit-based vinegar for cocktail mixing. There’s even one made from sake lees, the unfermentable dregs collected from the bottom of sake brewing tanks. more ›