The invention proposes to dispense a substance from a container (1) filled with a single portion of a substance. The container comprises a preformed deformable body, preferably made of sheet material, defining a filling cavity which body has an opening (6) and an integral planar circumferential rim (5) surrounding said opening, which opening is closed by a cover sheet (7) which is sealed to the circumferential rim (5) by means of a circumferential sealing seam (10). The container with the substance is opened by making use of the deformability of the cover sheet (7). A support surface supports the cover sheet (7) except at the position of a recess (10b). The recess (10b) is positioned at least over a part of the circumferential sealing seam. Upon compression of the container body the substance is pressurized and the cover sheet (7) bulges out into the recess (10b) such that the sealing seam (10) is broken at the location where the bulge is formed resulting in the container being open.