Abstract: A cover for openings in containers such as plastic or paper cups used, primarily, in fast food restaurants. The cover may include at least one one-way valve mechanism or be made of a porous material that allows air through but not liquids. An orifice with a tubular extension attached thereto provides a suitable engagement with a straw that is used to withdraw the liquid contained on the cup. Anchorage members are provided on the upper surface of the cover so that the straw may be bent when not in use.