Combine cake mix and milk in a blender and mix on low speed until fully combined.
15.25 oz Funfetti cake mix, 2 ½ cup milk
Gently fold in the whipped topping and rainbow sprinkles.
½ cup whipped topping, ¼ cup rainbow sprinkles
Distribute the mixture into the popsicle molds.
Freeze for at least 5 hours or overnight.
Video
Notes
If your mold is plastic or metal, you may want to omit the whipped topping. It can be difficult to pull out of the mold. Instead, you can use heavy whipping cream or yogurt. The general idea is to have 3 cups of milk, yogurt, or whipped cream to mix with the boxed mix.