Abstract: A cover includes an aperture for a straw, so that the cover can be used with a liquid beverage. The cover is elastically stretchable, and has a central body portion and an outer periphery. The cover can be stretched over an opening of a container so that the central portion covers the opening of the container while the periphery grips the outer side walls of the container. The aperture preferably is in a closed or nearly closed condition, such that insertion of a straw therethrough opens the aperture which then elastically retains the straw in an inserted position and provides a seal. This permits a user to consume the beverage, while still having the beverage protected against contamination or adulteration by drugs, dirt, dust, biologic matter, and the like. The cover is convenient, inexpensive yet effective, and readily portable.