And some medicines remain potent longer if their active ingredients are kept separate from the liquid until just before being taken. To take advantage of these factors, engineers at Erie Plastics, Corry, Pa. (erieplastics.com), have come up with Pop N’ Shake, a four-piece cap that stores the active ingredients, flavorings, or whatever beverage makers want to keep separate from the rest of the liquid. Just before drinking, the user removes the tamperproof dust cover and presses down on the cap, breaking a foil seal and letting all the ingredients combine. Shaking mixes them all together. The caps come in 26 and 38-mm sizes and can hold powders or liquids.