This is an instructible that doesn't work completely like the ones from the stroe but its alot cheaper!
Step 1: Get what you need
you will need
4.a rubber band
Step 2: Drill a hole in the can
get the can and remove the lid if there is one.Now flip it upside down and
drill a hole about 3/4 inches big in the center.
Step 3: Put on the balloon
strech the balloon over the top of the can where the lid would go.
Step 4: Put on the rubber band
now after putting on the balloon, take the rubberband and tightly rap it around until the
balloon is totally secure.
Step 5: Firing
now to shoot the air-zooka, pull back the balloon and let go. if the balloon breaks
then add a new one and if this doesn't work try to make the hole a bit bigger and if
that doesn't work than just go buy one.
If you feel like you could add a handle too.