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.
The thing is that mass-produced plastic items (like the plastic fish in question) are typically not produced with 3D-printing, because that would be incredibly slow and inefficient.
Instead, basically some kind of oil or molten mass is pressed into a form and then cooled down/condensed into a solid object. This way you can rapidly produce thousands of plastic items per minute. There is no nozzle involved, and you can do with fewer additives because the mechanical press removes the need for the filament to be so fickly 3D-printable. It can basically do with a bit more crude types of plastics, so you need a bit less additives to make the plastics more mendable.
I never said that these should be produced via 3D printing, it would be both economically unfeasible, and very difficult to achieve food safety, as I have mentioned.
The process you are describing is injection molding, generally used for solid parts. In this case, a variation called blown injection molding, is used. In this case the material is injected into a mold, and then a gas is blown into the interior, to make the material stick to the inner mold, and create a cavity. Nozzles are involved, as they are used to inject the material into the mold. These nozzles can be made specifically to be food safe, with stainless steel, for example.