Pour in vodka, Cointreau, cranberry juice, lime juice, and simple syrup.
Shake vigorously for about 15 seconds until the shaker is cold.
Strain into a chilled martini glass.
Garnish with a lime twist or wedge on the rim.
Notes
Use fresh lime juice for the best flavor. Adjust simple syrup to balance sweetness. Chill glass beforehand for a crisp, refreshing drink. Substitute triple sec if Cointreau isn't available.