In a 12-ounce, Collins-style glass, dissolve sugar in 1/2 ounce bourbon. Add mint and bruise gently with muddler or wooden spoon. Fill the glass 2/3 with crushed ice and mix gently. Add more ice and remaining bourbon. Top with sparkling water and stir. Rub rim of glass with lemon twist, squeeze mint sprig slightly, and insert stem into ice. Dust top of drink with confectioners' sugar. Insert 2 straws into ice so drinker must bury nose in mint in order to sip drink.