sad man in bar

A bum walks into a bar with only $6.00 . The guy decides to buy a pitcher of beer. He buys it and drinks about half of the drink. The man wants to go to the bathhroom but he doesn't want anyone to drink his beer so he takes his cardboard and marker and writes, "I have spit in this drink so do not drink it." He then goes to the bathroom and comes back to see that there is another sign just like it next to his. It says,"So did I!"