The old adage "If it sounds too good to be true it probably is" no doubt is accurate, especially when it comes to cleaning methods that take no work on your part. Store shelves are stocked with automatic toilet cleaners that claim to clean your toilet day and night while you sleep, work, watch Netflix, or do anything but polish your porcelain. Sure, your toilet is being sanitized, but at what cost? The drop-in toilet clean tablets are one of the worst things you could do to your toilet. The bleach in these tablets cause rapid rotting of the working parts inside your toilet tank; causing your toilet to run, leak, or not flush properly. The headache and cost of replacing these parts is much greater than the effort in elbow grease you'd have to put in to keep your bowl shining.
A little history:
In the 1990's, after these tablets were introduced, toilet manufacturers noticed an increase in repair calls on new toilets. It was discovered that the chemicals in the drop-in cleaner tablets will eventually damage the flush valve, flapper and other parts in the tank. Eventually toilets leaked or didn't flush properly due to the damage caused by the in-tank tablets. Toilet manufacturers are now putting warning labels on their products that "damage caused by in-tank tablets will not be covered under product warranties and should not be used.