Fluid flow control apparatus for use with fluid valves are disclosed. An apparatus includes a plug for a sliding stem fluid valve. The plug has a first portion slidably coupled to a second portion. The apparatus also includes a cavity formed in an outer circumferential surface of the plug by the first portion and the second portion. A dimension of the cavity changes when the first portion slides relative to the second portion to displace a seal disposed in the cavity. The seal sealingly engages a cage of the fluid valve when the second portion contacts a seat of the fluid valve.