A container providing for the separate storage of two materials and the admixing of the materials upon opening of the container. A main container holds a quantity of a first material, such as carbonated water, and a separate compartment holds a small quantity of a second material, such as a dipeptide sweetener flavoring. The disclosure provides several embodiments of the invention wherein a bottle has a compartmented closure applied as a cap thereto. The closure incorporates a compartment, which may be substantially cylindrically shaped, for the second material, and has a flexible top wall and a releasable bottom wall which is positioned within the neck of the bottle. An actuating rod extends through the compartment intermediate the flexible top wall to the releasable bottom wall whereby, when it is desired to admix the first and second materials, the flexible top wall is pressed down to force the actuating rod against the releasable bottom wall, thereby causing it to pivot open and release the second material within the compartment to admix with the first material in the bottle. In another embodiment of the invention the container is a can having a pull-top type opener, and in which a separate compartment in the shape of a cup is attached to the bottom of the can top closure beneath the pull-top opener and a dispensing orifice covered by the opener. As the pull-top opener is pulled open, the separate compartment tilts away from the can top closure into the container thereby releasing the second material into the can while freeing the dispensing orifice.