Welcome to our Prank War :)?

Me and my friend john are in the middle of a prank war. It started when he spit in my shoe, so i cooked macaroni noodles and dumped them in his back pack when he wasn't around. Today he taped the top of a spray-on deoderant down and hide it in my back pack. So now its my turn to get him back. I thought about putting kool-aid powder in his workout gloves and socks so his hands and feet would turn purple but im not sure if i'll do that just yet so i was wondering if yall have any good prank ideas?