I can't remember exactly where I was - either volunteering at the American Red Cross or at a hospital but I was in desperate need of a hair tie. I learned this hair tie life hack from a nurse.
She grabbed a latex glove like one of these.
She grabbed the end of the glove (opposite the fingers side) and ripped it off.
You end up with this - it's like a rubber band!
Pull your hair back with it and you're good to go!
I never thought I'd use this life hack again but it came in handy at the gym of all places. I forgot a hair tie and asked the front desk for one. The guy opened a bunch of drawers and didn't find any. I spotted a box of latex gloves and asked for a glove. Problem solved!