A spray gun (1) has a fluid reservoir (11) with a removable liner (13) received in a container (12) having a detachable lid (15). The liner (13), which may be thermo/vacuum-formed from a planar material, has a shape that corresponds to and is a close fit within the interior of the container (12) and collapses as fluid is withdrawn from within the liner (13) during operation of the spray gun (1). The lid (15) has an outlet (16) connected to an inlet on the spray gun (1) for transfer of liquid from the reservoir (11) to the spray gun (1) and the container (12) has a vent (12A) in the base end for admitting air between the container (12) and the liner (13) as liquid is withdrawn from within the liner (13).