A sealed reservoir cap for attaching to a bottle comprising: a first hollow part capped at one end thereof; a second hollow part having a seal closing one end thereof and slidably receiving the first hollow part therein with the punchable seal axially opposite from the capped end to define an enclosed reservoir therebetween, and having a barrier surface at or near a compartment opening of the second hollow part; an annular part disposed around the outside of the second hollow part to define a second annular space between the annular part and the second hollow part, the annular part formed with threads extending around its inner diameter to threadably engage the bottleneck of the bottle in the second annular space and dispose the punchable seal within the bottle; characterized in that the first hollow part is formed with a first protrusion on its outer diameter and a first recess, wherein said first hollow part includes a ring near or adjacent to the first protrusion; and the second hollow part further comprising: a second protrusion around an inner diameter and a second recess to receive the first protrusion therein, the first and second hollow parts defining a first annular space therebetween sealed by engagement of the second protrusion against the first recess on the outer diameter of the first hollow part; and a notched groove, wherein the notched groove is adjacent to the barrier surface and is arranged to receive said ring. a first hollow part capped at one end thereof; a second hollow part having a seal closing one end thereof and slidably receiving the first hollow part therein with the punchable seal axially opposite from the capped end to define an enclosed reservoir therebetween, and having a barrier surface at or near a compartment opening of the second hollow part; an annular part disposed around the outside of the second hollow part to define a second annular space between the annular part and the second hollow part, the annular part formed with threads extending around its inner diameter to threadably engage the bottleneck of the bottle in the second annular space and dispose the punchable seal within the bottle; characterized in that the first hollow part is formed with a first protrusion on its outer diameter and a first recess, wherein said first hollow part includes a ring near or adjacent to the first protrusion; and the second hollow part further comprising: a second protrusion around an inner diameter and a second recess to receive the first protrusion therein, the first and second hollow parts defining a first annular space therebetween sealed by engagement of the second protrusion against the first recess on the outer diameter of the first hollow part; and a notched groove, wherein the notched groove is adjacent to the barrier surface and is arranged to receive said ring. a second protrusion around an inner diameter and a second recess to receive the first protrusion therein, the first and second hollow parts defining a first annular space therebetween sealed by engagement of the second protrusion against the first recess on the outer diameter of the first hollow part; and a notched groove, wherein the notched groove is adjacent to the barrier surface and is arranged to receive said ring.