Disclosed herein is bottle cap which has a spraying unit or a nipple cap, with a space defined therein to contain an additive, such as a detergent, brightening agent or powdered milk. The bottle cap includes: an immobile unit having a guide part tightened to the mouth of a bottle body, and a chamber part inserted into the mouth, with a breaking tip and a through hole provided in the bottom of the chamber part, and a pipe part provided along the central axis of the chamber part; a storage container having a cylinder part inserted into the chamber part, a breakable film covering the open lower end of the cylinder part; a hole extending through the storage container and receiving the pipe part therein; and an externally threaded part extending upward from the upper end of the cylinder part and engaging with the guide part; a spraying unit having a cap part tightened to the externally threaded part, and a conduit pipe inserted into the pipe part. A spacing band is assembled around the externally threaded part at a position between the guide part and the cap part, thus spacing the spraying unit apart from the immobile unit by a predetermined interval. The spraying unit may be replaced with a nipple cap.