First you need to make hydrogen gas which require a few material. Such as a glass bottle, a Full table spoon of aluminum (beer or soda can will work), a half a cup of cold water, a table spoon or two of caustic soda, a funnel, a medium size container of water, a way of cutting the aluminum, one or two balloon's, and some safety glasses just incase something goes wrong.
Begin by cutting the aluminum into small snips until you have about a tablespoon, then put it into the glass bottle. Put in your one and a half table spoons of caustic soda, just enough to cover the aluminum so you may need more than what's listed. Now add the half cup of cold water and the mixture will begin to start fizzing. Once the mixture is fizzing put the balloon on top of the glass bottle, you will notice the bottle is getting warmer. Which is why you have the container of water, you put the bottle in the water, but try not to submerge the entire bottle in. Dip it in slowly so that it doesn't slow the process down entirely. Now just watch what happens, Be careful and have fun.
Have an iPhone? Check out all 200+ new features coming in iOS 13.