A method for dispensing a sample of liquid from a sealed thermoplastic container which includes both a volumetrically flexible chamber holding the liquid and also a plurality of spaced axially vertical nozzles on the container underside, the nozzles having an inlet in fluid communication with the chamber. The container is first manipulated to increase the volume of the chamber, rotated from a right side up position to an upside down position, and after the two preceding operations an axial opening is non-invasively created in the nozzle while the container is upside down without decreasing the volume of the chamber. The container is then rotated from the upside down position to a right side up position without decreasing the volume of the chamber, manipulated to decrease the volume of the chamber and expel a sample of the liquid from the chamber through the nozzle opening, then rotated to an upside down position and the opening in the nozzle is closed by melting and clamping it closed.