This trick is all about functionality over form. If you use wireless headphones but need them to work for several hours without needing to recharge, Redditor Aldorf suggests attaching a lightweight power bank to the headband.
Adhesive velcro on both the headband and the external battery pack will get the job done, as long as you make sure your cord is long enough.
Admittedly, this isn't going to make you look too good and it's not something you'd want to be strutting around in public with; in fact, Aldorf has copped a lot of flack for it. But if you're using your headphones at home and want the mobility to move around freely without worrying about charging them, then this is a simple trick and worth the convenience.