1. A vocal container cap comprising a hollow cap portion having a predetermined length to define a solid top and an open bottom, and a vocal assembly fitted in said hollow cap portion; said cap portion being provided at a distance below said solid top with a threaded section for engaging with external screw threads provided around a container mouth, and below said threaded section with a circle of weakened section for easily breaking said cap portion thereat when said cap portion is twisted relative to said container mouth; and said vocal assembly including a fixed member, a movable member located above and associated with said fixed member, and a mini speaker, an elastic switch, a circuit board, and batteries sequentially mounted between said movable and said fixed members from top to bottom, and a spring located between said movable member and said circuit board; said fixed member including a hollow ring portion having a plurality of windows spaced along a peripheral wall thereof, and a hollow plunger portion downward extended from a bottom of said ring portion for inserting into and sealing said container mouth; and said movable member including a diameter-reduced peripheral wall portion adapted to locate in said hollow ring portion of said fixed member and provided with a plurality of suspended tongues corresponding to said windows on said fixed member, such that a hook at a lower end of each said tongue outward projects into one said window and is normally pressed by said spring against an upper edge of said window; said cap portion with said vocal assembly received therein and fully closed onto said container mouth being located at a first position in which said spring between said mini speaker and said circuit board is compressed, said hooks of said movable member are lowered from said upper edges of said windows on said fixed member by a predetermined distance, and said vocal container cap is disabled; and said cap portion with said vocal assembly received therein and broken at said weakened section to loosen from said container mouth being located at a second position in which said spring lifts said movable member to actuate said vocal container cap.