Soda Seal Bracelets
also known as fuck-me bracelets 

When the top of a soda bottle cap's blue seal is taken out. Then the middle is removed, and the bracelet is stretched to fit around one's wrist. 

If you're wearing one and someone rips it off, it means you have to do the dirty with them.
I don't wear soda seal bracelets, they'd make me look like a skank.