An attachment for a beverage container may include a cap configured to attach to an opening in the beverage container. The cap includes an opening. The attachment also include a tube passing through the cap. A beverage in the beverage container can flow through the tube and out of the opening in the cap. The attachment also includes a container attached to the tube and configured to hold a liquid. The container includes an opening to allow the liquid to flow from the container into the tube and out of the opening in the cap. The attachment also comprises a restrictor between the opening of the container and the tube, such that the liquid begins to exit the opening in the cap before the beverage begins to exit the opening in the cap.