Abstract: An improved drinking-beaker assembly is provided which serves as both a drinking vessel, especially the drinking of water in the course of a diet, and a device for determining the precise amount of liquid consumed. The assembly preferably includes a beaker, a snap-ring collar, indicia for the number of uses and indicia for the volume level within the beaker. The beaker has a base, a wall and an open top. Portions of the wall define an annular groove having an upper rib, a bight and a lower rib. The collar is snugly fitted within the groove for manual, axial rotation of the collar relative to the beaker. The collar further includes a window which is aligned with the use indicia to sequentially indicate the number of consumptive uses of the assembly.