Abstract: An insert for placing in a bottle mouth for providing an improved interface for a person drinking a liquid from the bottle. According to one aspect, the insert has a flexible and resilient outer perimeter dimensioned so that the insert is an interference fit with the mouth of the bottle. The resilient and flexible characteristics allow a user to force the insert into the bottle mouth, thereby accommodating a range of bottle mouth sizes. A preferred insert material has a durometer in the range of 60-80. The insert is configured so that when installed in the bottle mouth, a first opening is provided for drinking that is smaller than the bottle mouth. The insert also provides for air intake into the bottle by way of either a second opening or an extension of the first opening.