In a medium to large mixing bowl, stir together the sweetened condensed milk and Kool-Aid packet.
Then, fold in the cool whip until well combined.
Spoon the mixture into the pie crust, smoothing the top.
Cover and refrigerate for at least 2 hours or overnight.
Notes
A flexible, rubber spatula is best for folding in the whipped topping and smoothing the filling into the crust.
Before serving add any toppings you prefer, like fresh fruit.
This pie will become softer as it warms, so if you are serving this outside (like at a picnic) keep it in a cooler or refrigerator until you are ready to serve.
Kool-Aid pie leftovers can be stored in the refrigerator and eaten up to five days after it's made. The flavor of the Kool-Aid may deepen over time.