5 cups hot water
1 (6 ounce) package strawberry-flavored gelatin mix (such as Jell-O®)
1 pint vodka
1 (12 fluid ounce) can frozen lemonade concentrate
1 (12 fluid ounce) can frozen orange juice concentrate
1 (2 liter) bottle lemon-lime soda (such as 7Up®)
Combine hot water and gelatin in a large bowl; stir to dissolve.
Mix vodka, frozen lemonade concentrate, and frozen orange juice concentrate into the dissolved gelatin. Ladle slush mixture into freezer-safe containers; freeze for at least 24 hours.
Scoop frozen slush into glasses with an ice cream scoop; top with lemon-lime soda.