Take your water balloon fight to the next level by filling balloons with colorful Jell-O. Just make sure this fun but messy activity is played outdoors, in play clothes you don’t mind staining.

Materials:
Boxes of Jell-O
Funnel or turkey baste

Directions:
Follow the directions on the Jell-O box to make the gelatin, but before chilling, use a funnel or turkey baster to pour (or squirt) the Jell-O mixture into the balloons. Place the balloons carefully in a fridge to set. Surprise your kids with a sticky balloon war. 

Source: Sandi Haustein, “Say ‘Yes’ to the Mess,” Atlanta Parent, Aug 2013.
Check out the other 65 Days of Summer Fun ideas here.