Exemplary embodiments include an apparatus that can be connected to a valve on a keg, such as a Sankey-D valve, and can be used to add gas into the keg to mix the contents, which may be including alcoholic spirts and a non-alcoholic drink mix. The apparatus has an upper structure which is coupled to a lower portion configured to mate with a keg valve. The filling apparatus may be designed to depress the ball valve and ring valve portions of the keg valve to allow for both the addition of gas and venting of gas from the keg simultaneously.