Chill a Martini glass or coupe cocktail glass by placing it in the freezer so that your drink is ice cold; or fill the glass with ice and let it sit while you make the cocktail.
Optional: Rim your cold glass with lemon slice juice, and dip it in granulated sugar; set the prepared glass aside.
In a cocktail shaker with ice cubes, combine the vodka, triple sec, lemon juice, and simple syrup.
Shake vigorously until well-chilled.
Use a cocktail strainer to strain into the prepared Martini glass/coupe glass with sugar (if you chose to use it).
Optional: Garnish it with a lemon twist or a hint of lemon zest across the top.