We needed lots of candy in our balloons for our balloon pinata. Our first attempts, just opening the neck of a standard latex balloon and shoving in as much candy as we could, averaged about 3 to 4 pieces before we poked a hole somewhere. My husband then decided it was time for a new plan and a trip to Home Depot.
The basic concept is to create a vacuum so you can expand the balloon, insert your candy, and then slowly deflate the balloon. This was the method my husband came up with, but you could make a vacuum any number of ways. You'll need a wet/dry vacuum, and a few other items: a 4" PVC pipe elbow, a 4" rubber end cap, a piece of PVC coupling that's big enough for your candy to pass through, a 4" to 2" reducer, and a little valve to help control the airflow. (All this will run you about $20, assuming you have a vacuum.)
You can see everything in the photo above. Starting from the left side: the valve (attached to the wet/dry vac), some PVC pipe, a 4" to 2" reducer (the black funnel-like piece), and a 4" elbow piece of PVC pipe.
You need to cut a hole in the rubber end cap (the black piece on the bottom right) to fit your 2" PVC coupling. This is what you will feed your candy through.
Once you're all assembled, stretch the neck of the balloon over the 2" pipe coupling. Then slide the rubber end cap onto the elbow piece, with the balloon inside the elbow.
Now the tricky part: You need to open up the valve just enough to create a vacuum and expand your balloon. It's all about pressure, you need a decent amount of pressure to expand the balloon, but if you use too much, it will pop.
It's probably not a perfect seal, so you need to maintain the vacuum with a certain amount of pressure to keep the balloon blown up. JR found it helped to manually tweak the pressure by holding the joint between the valve and the wet/dry vac hose (see photo below).
Once your balloon is expanded, grab your candy and drop it piece by piece through the 2" piece of coupling (we made ours big enough to fit our biggest piece of candy, a box of Nerds). We found 13-15 pieces of candy worked well, when we tried to do more we usually popped our balloon. Then slowly tweak the pressure so the balloon deflates around the candy.
When you open up the rubber end cap, you'll see all the candy with the balloon deflated around it. We then used a small hand pump to blow up the balloons to the desired size.
We blew our balloons up the night before the party and kept them in a large trash bag. Once we were at the park ready for the party, we staple gunned the balloons to a big wooden board (we covered ours with a plastic tablecloth to avoid splinters).
One at a time, each guest at the party stood about 5 feet in front of the board and threw a dart at the balloons, trying to pop one. The balloon would pop, and the candy would explode, and the child got to run and grab all the candy from their balloon. The kids loved it, and even the littlest guys who were 4 and 5 years old could pop a balloon pretty easily.
Thanks for figuring this one out JR. I love the crazy way your mind works.