Toasting with Water
Clinking glasses with water in your cup has been bad karma since the ancient Greeks who only toasted with water to honor the dead.
The idea started with the myth that the dead drank from the River Lethe in the Underworld to leave behind their corporeal lives.
This toasting tradition evolved over time into a superstition that you are wishing bad luck (or death) upon someone when you cheers with water in your glass.