Hydrogen for balloons/blimps from zinc and hydrochloric acid, simple setup.
An easy way to make hydrogen using hardware store muratic acid (hydrochloric acid ~30%) and zinc metal. New pieces of zinc go in through the second lower opening. It produces a lot faster when there's more than 1 tiny piece of zinc in there like in this test run.
The water bottle bubbler is to cool down the hydrogen and remove hcl fumes. The balloon envelope is heat fused (clothing iron on top of parchment paper) plastic painter's 0.7mm drop cloth.