A lid assembly configured to close an opening in a vessel holding a liquid. The lid assembly includes a drinking port, plunger member, and drive assembly. The plunger member is moveable between closed and open positions with respect to the drinking port. The plunger member prevents the liquid from flowing through the drinking port when the plunger member is in the closed position and allows the liquid to flow through the drinking port when the plunger member is in the open position. The drive assembly includes drive circuitry that automatically directs the drive assembly to move the plunger member to the open position when the drive circuitry detects the lid assembly is in a drinking position. The drive circuitry automatically directs the drive assembly to move the plunger member to the closed position when the drive circuitry detects the lid assembly is in other than the drinking position.