A mixing assembly comprises a coupler with a temporary seal that is connected to a first container containing mix ingredients. An internally and externally threaded insert is threadedly mated with the internally threaded coupler in an initial position short of breaching the temporary seal. A second container is screwed into the internally threaded insert. Sealing relationships are formed between the coupler and the insert, and between the insert and the received second container. Once the second container is secured to the insert, the coupler is screwed downwardly toward the insert to cause the insert to threadedly advance toward and eventually breach the temporary seal to enable contents of the first container to mix with that of the second container.