An attachment (1) for a bottle which holds a first liquid, wherein the bottle has a bottle opening and is surrounded by a wall, and wherein the attachment is delimited from the surrounding area by an outer wall (18) and has a bearing surface (2) for bearing sealingly against the bottle, a reservoir (4) which is designed to hold a second liquid, a channel (6) which connects the bottle opening to an outlet of the attachment, and a passage (20) which connects the reservoir to the channel. In order to ensure secure fastening of the attachment (1) to the bottle, the attachment is designed to be attached concentrically to the bottle outside of the bottle opening and the attachment has a bearing surface which is provided with a seal (12).