Sprinkle sugar on a small plate. Lightly wet half the rim of of a coupe glass with a damp paper towel. Dip the moistened rim in sugar to coat. Set the glass in the refrigerator to chill.
Combine Cognac, orange-flavored liqueur, and lemon juice in a cocktail shaker. Add ice, cover, and shake until chilled. Strain into the chilled, sugar-rimmed coupe.