Abstract: In a mixing system for mixing together a powdered beverage and a liquid in-situ to form a ready-to-drink beverage, a receptacle has an interior space defining a mixing chamber for receiving powdered beverage and liquid therein to be mixed. An agitator is removably disposed in the mixing chamber, the agitator being operable to mix the powdered beverage and liquid within the mixing chamber, said agitator being removable from the receptacle. A retention member is configured to inhibit the agitator against falling out of the receptacle upon substantially inverting the receptacle. A drive system is provided for operating the agitator, with the agitator and drive system being configured for operative coupling therebetween. The mixing system may include a support for supporting the receptacle in an upright orientation. The receptacle may be removable from the support. The agitator may include an anti-vortex member to inhibit formation of a vortex.