If you are a superstitious one, toasting with a glass full of water is probably one of the worst things you can ever do.
Making a toast itself is hard, and in weddings, we always make a toast with wine in our glasses. But did you know that it's bad luck to do so?
In Ancient Greece, the Greeks believed that the dead would drink from the River Lethe in the Underworld in an effort to forget the past lives and move on. As a consequence, the Greeks would always offer a toast with water in their glasses to send of their dead, a symbolism of their voyage.
So when you propose a toast to someone with water in your glass, its like wishing bad luck, and maybe worse, death, on him or her. Some even go to the extent to believe that you might wish death upon yourself, since this liquid reflects your watery grave in the future.
Other than wishing your guest of honour and yourself death, toasting with water will also anger the Gods. Making a toast symbolised a wish you were making to the Gods, whenever you raise the glass you offer a drink to the Gods. Celebrating with water, was not appreciated by the Gods, since it was a dull and neutral drink. They would then shower down ill fortune on anyone who dared to do so.