The balloon won't blow up as if you had blown air into it with your mouth, but it will go from being limp to being erect. Use an empty soda bottle. A glass one would be more stable. Put in a teaspoon of baking soda. Now put the balloon over the mouth so as to practice and loosen the neck. Remove the balloon and, here you will need to move fast, pour in 2-3 ounces of clear vinegar and quickly replace the balloon. The CO2 released will puff up the balloon. You might make a video of it. Good luck.
Gather your materials: a narrow mouthed bottle (yes, glass is better), a balloon, vinegar and baking soda. Use a funnel to put baking soda into the balloon. Pour vinegar into the bottle. You can experiment to see what amounts work best, but in order to make enough gas to blow up the balloon, I'd try about 1/2 cup of vinegar, and baking soda to fill the balloon to the base of the neck. Next, put the balloon onto the neck of the bottle WITHOUT letting the baking soda fall in, let it flop over so it cannot fall into the bottle until you are ready. When everything is in place, lift the base of the balloon so the baking soda falls into the vinegar in the bottle. Swirl the bottle a little, to help it mix. The balloon will inflate part way.
You take a 1L bottle and you put vinegar into the bottle. When you are done doing that you fill a balloon with baking soda. After you are done you carefully place the balloon neck into the bottle neck without spilling any of the baking soda into the vinegar. When you are done shake the bottle with the balloon and let the baking soda into the vinegar. Observe what happens. Im I right?