Pour the Kool Aid powder, sugar, and water into a large mixing bowl.
Whisk or stir vigorously until the mixture is bright and evenly combined, with no lumps.
Pour the mixture into a freezer-safe container, spreading it out to ensure quick freezing.
Place the container in the freezer and let it freeze for about 1 to 2 hours.
Check the mixture every 30 minutes, stirring with a fork or spoon to break up ice crystals and promote a smooth consistency.
Continue stirring every 30 minutes until the slushie reaches a soft, scoopable texture, about 3 to 4 hours total.
Scoop the bright, flavored slushie into glasses or cups and enjoy immediately for the best texture and flavor.