Car Owners Hub UK - Built by Drivers, for Drivers

Bitrex is a coating on some coin cell batteries; it tastes bitter. (It's a move to foil Darwinism and spare the lives of the ignorant!) The batteries will no longer function correctly due to the reduced current. Before installing a battery, it is always a good idea to wipe it down with an alcohol wipe to remove any coating.

I thought you might find it amusing that some people are so naive that they leave coin batteries in key and actual coin dishes, BB. For children, these appear appealing. A child's gullet can be rapidly and fatally burnt by a battery cell. For the sake of safeguarding children from careless adults.