1 (2 liter) bottle lemon-lime soda (such as 7-Up®), divided
Instructions:
Combine limeade concentrate, vodka, green food coloring, and 1 1/2 liters of lemon-lime soda in a large plastic container with a lid. Freeze the mixture for 1 to 3 days, then scoop the frozen slush into glasses and top off each glass with a splash of lemon-lime soda.