Quickly pull the cookie sheet straight out from under the cup and observe the fall of the cup and water. If the cup were slowly pushed over the edge of the sheet, the water would pour out. However, when the sheet is quickly pulled out from under the filled cup, the cup and water both fall at the same time. Since they are both accelerated downward by gravity an equal amount, the cup and water fall together. The water remains in the cup but the lower surface of the water bulges.
Surface tension tends to draw liquids into spherical shapes.
When liquids are at rest, gravity overcomes surface tension, causing drops to spread out. In freefall, gravity's effects are greatly reduced and surface tension begins to draw the water in the cup into a sphere. Close the hole with your thumb and fill the can with water. While holding the can over a catch basin, remove your thumb to show that the water falls out of the can. Close the hole again and stand back about 2 meters from the basin.