I have a device that charges via 3.5mm audio jack, except it's not audio, but 5V.
It's not entirely bad idea given how annoying micro USB and USB-C are to implement.
However, I've lost the one-of-a-kind USB-to-3.5mm-jack cable and I'm mildly annoyed I'll have to make one myself.
@robryk there are jacks with two rings (with mic and/or buttons) so data could go over the rings.
I've tried gnd on the sleeve and 5V on the tip. Will see if that works.