I'd get a soup plate and then slide the glass very carefully over to the edge of the table, and let the water run into the soup plate - it doesn't have to run onto the floor.
They studied it a little bit, but they couldn't spend all day finding out what to do, so they finally picked up the other one, and the water went out again, all over the floor.
If the tip was a dime in one glass, the waitress, in her haste to get the table ready for the next customer, would pick up the glass, the water would spill out, and that would be the end of it.