An apparatus for hot or warm filling comprising a compression machine configured to apply an axial compression force to a collapsible thermoplastic container for liquids. The compression machine includes a lower body having a surface designed to be a resting surface for the base of the container; at least one upper body designed to contact a portion of the container above the peripheral groove, so that the container can be held in an upright position by the at least one lower body and the at least one upper body; actuating means for actuating the at least one lower body and/or the at least one upper body in order to apply said axial compression force, acting along a direction parallel to the longitudinal axis of the container, in order to make the proximal straight side to come into contact with the distal straight side, thus reducing the internal volume of the container.