My dad did this once. He drained the acid from a car battery and put it in a container with a narrow opening, then dropped in a bunch of zinc galvanized nails. Sulfuric acid + zinc = hydrogen gas. He then stretched balloons over the mouth of the container to inflate them, tied them up, and attached a strip of newspaper to the bottom. Finally, he lit the bottom of the newspaper on fire and let it go. Balloon floats up, makes pretty fireball.
We ran into two problems. First, a number of the flames blew out on their way up. No fireball.
Second, we ran out of balloons pretty fast. So he cast around for ideas, and decided to fall back on a box of condoms. They held a lot more hydrogen than the balloons.
They were also equally likely to go out before blowing up. I always imagined them coming down on someone's lawn, causing no end of confusion.
[DO NOT TRY THIS AT HOME! And if you're tempted, there's one thing I left out that's necessary for it to work properly, and the only thing I'll say about it is this warning: https://sciencenotes.org/add-acid-to-water-or-water-to-acid/ ]
