Formation fluid sample container apparatus are described. An example apparatus includes a downhole tool having a body including an opening and a cavity extending into the body from the opening. The sample container includes an elongated container for holding a formation fluid sample and a sheath coupled to an outer surface of the elongated container and at least partially surrounding the elongated container. The sample container is fixed in the cavity and the sheath is to increase the mechanical integrity of the elongated container in a downhole environment.