1 carton (8-oz) frozen limeade concentrate
1 pint lime sherbet + more for floating, if desired
2 cups crushed ice
1 lime, juiced
Combine half the Sprite or 7UP, the limeade, sherbet, and ice in a blender; pulse until blended and most of the ice is gone.
Transfer mixture to a punch bowl and add the remaining Sprite or 7UP and the fresh lime juice.
Float additional scoops of sherbet on the top, if desired.