Pour granulated sugar onto a small plate. Rub a lemon wedge around the rim of each shot glass and dip the rims into the sugar to coat.
Fill a cocktail shaker with ice. Add vodka, lemon juice, and simple syrup.
Shake vigorously for about 15 seconds until well chilled.
Strain into prepared shot glasses.
Garnish each with a small lemon wedge, if desired.