The device known as shoyu-tai (or soy-sauce snapper in Japanese) was invented in 1954 by Teruo Watanabe, the founder of Osaka-based company Asahi Sogyo, according to a report from Japan’s Radio Kansai.
It was then common for glass and ceramic containers to be used but the advent of cheap industrial plastics allowed the creation of a small polyethylene container in the shape of a fish, officially named the “Lunch Charm”.
The invention quickly spread around Japan and eventually worldwide, and it is estimated that billions have been produced.
I’ve never seen these things before but it does seem like a waste of plastic. Even sachets of sauce shouldn’t be handed out in most circumstances, at least for dine-in food in fast food places - use dispensers and paper cups. I wonder if there is a biodegradable sachet material which has a couple of years shelf life but degrades thereafter.