A fluid reservoir for storing a fluid for a handheld device includes a housing and a flexible membrane. The flexible membrane delimits a variable storage volume in the housing. The storage volume may be varied by a defamation of the membrane. The variable storage volume has an output port. The fluid reservoir further includes a forcing member to exert a force on the membrane to pressurize a fluid in the storage volume. The forcing member has a recess for receiving a part of the storage volume. The membrane may be received into the recess of the forcing member during a compression stroke. By virtue thereof, a volume defined by the recess may be effectively used to become part of the storage volume for the fluid.