Secret Prank Gone Wrong

I did this dumb prank on my little brother yesterday. I filled his water bottle with soda and put baking soda in it to make a fizzy mess when he opened it. He was so mad, but the worst part? When he spilled it all over himself during karate class. Now everyone's talking about how stinky he smells from the soda pop. I feel bad for pulling such an immature prank, but I just couldn't resist seeing him get in trouble.