Ke$ha -- I Drank My Own Pee ... and It's On Tape

We now know why Ke$ha felt compelled to brush her teeth with a bottle of Jack ... 'cause the pop singer says she once drank her own pee!!!!

Ke$ha leaked the information to BBC 1 radio, saying she imbibed her own urine while filming an upcoming MTV documentary called "Ke$ha: My Crazy Beautiful Life."

The 25-year-old said her journalist brother filmed the doc over the last 2-and-a-half years, claiming, "He got all the things you would want to see and all the things you wouldn’t really want to see -- making out with dudes, drinking my own pee, jumping out of a building, jumping out of aeroplanes, swimming with sharks ..."

She added, "I was told drinking my own pee was good ... Somebody tried to take my pee away from me and I said, 'That is mine!' So I snatched it up and took a chug and it was really gross so I don't do it anymore."