This is an interesting as well as an intriguing Physics problem often confusing the students. I think students can explore their text books or help books to find out the solution of this.
Meanwhile as I have also read about this, I will like to explain it. The Earth rotation creates a drag on the air in the atmosphere and this effect is known as Coriolis force named after the scientist who discovered it and gave a detailed theory about this peculiar thing. The huge size of the Earth and equally huge atmosphere give rise to this interactive force generated through the relative motion.
That is the reason why during the hurricanes, the air in the atmosphere spins in a counterclockwise direction in the Northern hemisphere and clockwise in the Southern hemisphere.
Now coming to water which is spinning and going down the sink, seeing the small size of the sink and its geometry, the Coriolis force is so feeble and negligible that it can not do any movement in the water body.
So depending upon how you throw the water in it and the slope of the sink floor and other geometrical factors the water going down the sink can rotate in any direction. Coriolis force has nothing to do with it.
So water body in the sink can rotate in any direction.
Knowledge is power.