If you have a bunch of spare junk lying around, you can make a pretty weak phone charger, as Thomas Kim demonstrates.
Kim fashions an iPhone charger that uses wind for energy from the disassembled bits of a hair dryer, a cigarette-lighter socket yanked out of a car, a USB charger for said cigarette socket—plus a few other hardware odds and ends. He hangs it out of the window of a moving car (the only way to make this work, aside from running around with it held out like a selfie stick) to demonstrate its awesome wind-harnessing power: About 1% of juice every 10 minutes. A bigger fan could produce a faster charge.
In the realm of making semi-useful shit out of scraps, Kim’s prolific. Previous experiments include a butane gas candle and a homemade fireworks timer. “Most experiments are easy to try with household items,” Kim writes on his channel description. “But some experiments are very dangerous.” This one’s fairly safe, however. The biggest danger would be losing the whole getup out the window, phone and all.