A reusable cap for a container comprising a central body extending along a central axis with a lower end that is open and a top end that is closed by a top plate, wherein the lower end is rotatably engageable with the top end of a similar cap； a skirt that extends around the central axis to surround the central body with an inner edge adjacent to the central body and an opposing outer edge and is radially spaced from the central body by a plurality of tabs to form an open space allowing air passage； a plurality of external cooperating engaging formations on said skirt, wherein the plurality of external cooperating engaging formations comprise at least one male engaging formation and at least one female engaging formation； and wherein the male engaging formation is a protrusion extending radially outward from said skirt and the female engaging formation is defined by an indent.
