A cap for a container, comprising: a main body having a top plate and a circular sidewall, the top plate having a top surface, wherein two opposite sides of the circular sidewall circularly connect to each other, one periphery of the circular sidewall connects to one surface of the top plate forming a closed end, and the other periphery of the circular sidewall at the opposite side of the closed end forms an opened end (1"); and a ring member, which is located at the opened end of the main body; a first incision between the opened end of the main body and the ring member, the first incision having a first end and a second end, the first end being separated from the second end; and a second incision located on the main body or the ring member, the second incision having a first end and a second end, the first end of the second incision being separated from the second end of the second incision; wherein the first incision and the second incision do not intersect and are configured so that when the cap is on the container and the cap is unscrewed, the main body separates from the ring member except for a first connection portion and a second connecting portion formed by the first incision and the second incision; characterized in that a location and length of the first incision and the second incision are selected so that a length of the first connecting portion and a length of the second connecting portion are long enough to allow a user to, by an application of force, stretch the first connecting portion and the second connecting portion sufficiently to allow the main body to be placed into a flipped position where the top surface of the top plate faces toward the container, and so that the length of the first connecting portion and the length of the second connecting portion are short enough that the elasticity of the first connecting portion and the second connecting portion hold the main body in the flipped position once the user places the main body in the flipped position. a main body having a top plate and a circular sidewall, the top plate having a top surface, wherein two opposite sides of the circular sidewall circularly connect to each other, one periphery of the circular sidewall connects to one surface of the top plate forming a closed end, and the other periphery of the circular sidewall at the opposite side of the closed end forms an opened end (1"); and a ring member, which is located at the opened end of the main body; a first incision between the opened end of the main body and the ring member, the first incision having a first end and a second end, the first end being separated from the second end; and a second incision located on the main body or the ring member, the second incision having a first end and a second end, the first end of the second incision being separated from the second end of the second incision; wherein the first incision and the second incision do not intersect and are configured so that when the cap is on the container and the cap is unscrewed, the main body separates from the ring member except for a first connection portion and a second connecting portion formed by the first incision and the second incision; characterized in that a location and length of the first incision and the second incision are selected so that a length of the first connecting portion and a length of the second connecting portion are long enough to allow a user to, by an application of force, stretch the first connecting portion and the second connecting portion sufficiently to allow the main body to be placed into a flipped position where the top surface of the top plate faces toward the container, and so that the length of the first connecting portion and the length of the second connecting portion are short enough that the elasticity of the first connecting portion and the second connecting portion hold the main body in the flipped position once the user places the main body in the flipped position.