Adapter for a container, which adapter comprises: - a central body with a main axis and a fluid channel extending through the central body along the main axis, which fluid channel has on a first side of the central body a first opening for connection with a container and has on the opposite, second side of the central body a second opening for dispensing fluid from the container; - a sleeve arranged coaxially around the central body, wherein the sleeve is movable in the direction of the main axis between a closing position and a dispensing position, wherein the sleeve is fully rotatable around the main axis in the dispensing position, and wherein the rotation of the sleeve is blocked in the closed position; the sleeve comprising a cap portion arranged inside the sleeve, wherein the cap portion closes the second opening in the closing position of the sleeve and wherein the cap portion has at least one opening, which is in fluid connection with the second opening in the dispensing position of the sleeve wherein an annular space is formed between the sleeve and the cap portion for reception of a spout of a second container, wherein at least part of the wall of the annular space comprises connecting means, such as a screw thread; - at least one resilient finger arranged with one end to the central body and wherein the other end of the finger is provided with a hook-shaped end, wherein the hook-shaped end extends into the annular space in the closed position of the sleeve and hooks with a protrusion arranged to the sleeve and wherein the hook-shaped end is positioned outside of the annular space in the dispensing position. - a central body with a main axis and a fluid channel extending through the central body along the main axis, which fluid channel has on a first side of the central body a first opening for connection with a container and has on the opposite, second side of the central body a second opening for dispensing fluid from the container; - a sleeve arranged coaxially around the central body, wherein the sleeve is movable in the direction of the main axis between a closing position and a dispensing position, wherein the sleeve is fully rotatable around the main axis in the dispensing position, and wherein the rotation of the sleeve is blocked in the closed position; the sleeve comprising a cap portion arranged inside the sleeve, wherein the cap portion closes the second opening in the closing position of the sleeve and wherein the cap portion has at least one opening, which is in fluid connection with the second opening in the dispensing position of the sleeve wherein an annular space is formed between the sleeve and the cap portion for reception of a spout of a second container, wherein at least part of the wall of the annular space comprises connecting means, such as a screw thread; - at least one resilient finger arranged with one end to the central body and wherein the other end of the finger is provided with a hook-shaped end, wherein the hook-shaped end extends into the annular space in the closed position of the sleeve and hooks with a protrusion arranged to the sleeve and wherein the hook-shaped end is positioned outside of the annular space in the dispensing position.