These orange stink balls, pronounced “bohan” in Japanese, are balls filled with stinky orange colored liquid and are used for deterring and catching criminals in Japan.
They come in different colors, but the orange is the most popularly used. They are widely available for purchase online, and are most commonly found in Japanese banks gas stations and convenience store type places, next to each employees station. When someone is caught stealing or engaging and criminal activities, the tellers or attendants at the store will throw these at criminal.
The balls are filled with a thick fluorescent fluid that glows in the dark and stinks like rotting pineapples. The color staining the criminal if hit with one of these balls makes them stand out in a crowd, and the stink will too. Also, police dogs are trained to sniff out this particular oder and associate with a criminal, which also makes the perpetrators easier to find.
Watch a video below of a convenience store attendee explaining and accidentally demonstrating the use of one of these orange stink balls: