Stir together all ingredients until sugar is dissolved. Pour desired amount of mixture into a cocktail shaker filled with ice cubes. Cover with lid, and shake 30 seconds. Strain into chilled cocktail glasses. Repeat with remaining mixture. Serve immediately (or make ahead; see tip below).
Note: We tested with Cointreau orange liqueur.
Test Kitchen Tip: Mix up several batches of Pink Cadillac Margaritas 3 to 4 hours before the party starts, and chill in decorative bottles or pitchers, ready to shake and serve when guests arrive.