Abstract: The present invention relates to a mug, especially a disposable mug, which mug defines an internal space for receiving liquid. It is significant for the mug according to the present invention that the mug contains a flap (10; 110) provided on the inside of the mug, that the flap (10; 110) extends along the inside of the mug in a non-active state, and that the flap (10; 110) reaches out from the inside of the mug in an active state of the flap (10; 110).