In Italy, many years ago, when I was a kid, this fluoride bite was something that was given to us at (elementary) school, cannot remember if once or twice a year, they made a sort of quick medical checkup and while the doctor was visiting you, you had this bite.

But the practice was later abandoned, as it seems that the 6-8 age is the worst one to supplement (too much) fluoride, that could later develop in dental fluorosis:

https://en.wikipedia.org/wiki/Dental_fluorosis