A flow control device includes a hood, a ball valve, a sealing ring, and a handle. The ball valve is movably received in an interior receiving space of the hood and the ball valve is set in sealing engagement with the sealing ring. The ball valve and the handle located outside the hood are coupled together and are thus movable in unison with each other. The ball valve defines a flow passage. The hood forms a discharge opening. When installed on an opening of any kind of container, such as a PET bottle or a glass bottle, or an outlet tube of a water tank, by rotating the handle to move the ball valve, the flow passage can be selectively set in fluid communication with the discharge opening.