There is no crankcase drain. There are three ways to clear it that come to mind.
One, just keep trying and washing the plugs off each time they foul. Eventually it'll run, just smoke seriously for a while.
Two, take it outside, remove the plugs, put it on the center stand and in gear, then spin it as fast as you can using the rear wheel until nothing more comes out. You may have to put some gas in the crankcase through the carburetors to flush the oil if most of the fuel is already out.
Three, the 2-stroke woods rider's method of clearing water after a bad creek crossing - pull the plugs, turn it upside down, put it in gear and use the rear wheel to spin it fast. not so easy with a street bike.