A material is added to a container of liquid from a dispenser that fits onto an open mouth of the container. The dispenser has an open position and a closed position, and includes an outer shell and an inner chamber member within the shell. The shell and chamber member are mounted to rotate relative to each other to align openings therein when in the open position and through which the material exits the chamber member. The material is loaded into the chamber member, and subsequently the dispenser is sealed with a seal that is connected to both the shell and the chamber member to prevent relative rotation of the shell and chamber member and dispensing of the material. The dispenser is inserted into the open mouth, unsealing the seal, and rotating the shell and chamber member relative to each other to open the dispenser and allow the material to flow into the container and mix with the liquid therein.