Abstract: A drinking vessel includes a first receptacle having a first circumferential side wall extending from a closed bottom end to a shoulder having a peripheral edge defining a first diameter. An externally-threaded attachment portion, defining a second diameter smaller than the first diameter, extends from the shoulder to a circumferential lip. A second receptacle configured to fit inside the first receptacle has a second circumferential side wall extending from a closed bottom end to an upper rim defining an open top end. A circumferential flange, depending downwardly from the rim and fitting coaxially around the attachment portion, has a lower end separated from the shoulder by a circumferential gap. The flange has an outer surface and an internally-threaded portion that mates with the attachment portion. A resilient element has a grip portion fixed to the outer surface of the flange and a sealing portion configured to seal the gap.