A fluid transfer assembly and methods of fluid transfer is described. In one aspect, the fluid transfer assembly includes a fluid container having an opening in a bottom, a coupling device attached to the fluid container at the opening, and a filling device. The coupling device may include a valve biasing the coupling device in a closed fluid-tight position via magnetic attraction of opposing first and second components, each of the opposing first and second components including a magnetic material. The filling device may include a rigid member with a perimeter smaller than a perimeter of the fluid container opening, the rigid member including a passage along a longitudinal axis and one or more apertures through a sidewall in fluid communication with the passage, such that the coupling device is transitioned from the closed fluid-tight position to an open position by pressing the rigid member against one of the opposing first and second components, thereby placing the apertures in fluid communication with an interior of the fluid container.