A device aerates a drinkable liquid inside a handheld container. An aerator is detachably mounted on the container in a mounted position. The aerator has an aerator portion that extends into the liquid and that is held adjacent an interior surface of a side wall of the container in the mounted position. The aerator portion has a multitude of turbulence-inducing agitating elements, such as pores, through which the liquid in the container flows to, and impacts against, the interior surface of the side wall of the container, and mixes with ambient air in the container, when the container is manually swirled to aerate the liquid.