Abstract: A drinking vessel has a cup with a removable lid having at least one inlet-outlet opening which receives an elastic straw-vent assembly having a flexible tubular straw or spout and a ventilation member that defines an air passageway and a vent opening. A vent actuator is operably coupled to the ventilation member and configured to change a state of the ventilation member between a ventilation state and a closed state. A cover movably mounted on top of the lid, shiftable between a closed and an open position, comprises a cam on an inward surface of the cover which is configured to contact the vent actuator during movement of the cover member to change the state of the ventilation member. In the closed position the cover engages the straw, folding the straw against the lid, and in the open position, the straw fluid passageway and the vent opening are unobstructed.