1 fluid ounce vodka (such as Absolut®)
1 fluid ounce Blue Curacao
2 fluid ounces sweet and sour mix
ice cubes, as needed
1 splash lemon-lime soda (such as 7-Up®)
Pour the vodka, Blue Curacao, and sweet and sour mix to a cocktail shaker filled with ice; shake to chill.
Fill a collins glass with ice; strain the vodka mixture into the glass. Top with a splash of lemon-lime soda.