Thirst
(2008)

The four main characters crash their vehicle while in the middle of an uncharted part of the desert surrounding Death Valley.

In the car crash, one of the four, Atheria, gets a concussion which turns a hematoma, killing her.

After two days of waiting for rescue, including scouting for people and torching their broken vehicle as a signal fire, they finally decide, with no water left, to walk west, where a map shows there is a small town 25 miles away.

After two days of walking, they find a small pool of water. However, it is poisoned with arsenic (in the middle of the desert). Tyson decides to drink the water anyway, to test it. He dies in the morning from arsenic poisoning.

After another day of walking, Noelle (Lacey Chabert) and Bryan sit down to rest overnight. During this, Bryan slits his throat with a razor blade so Noelle can drink his blood to prevent her from dehydrating and walk to safety.

In the morning, day six, Noelle begins to walk again, only to find... their burnt truck. The whole time they were simply walking in a big circle. Noelle finds a coyote had dug up Atheria's grave, and was eating her body. Just then, she remembers that Atheria had breast implants, which are full of saline, which is basically water. Using the tire pump from the truck, she rigs an IV and, using the saline from Atheria's breast implants, injects herself with the water.

Rehydrated by the saline, she has enough energy to walk to a road, where a truck is seen driving towards her, and will presumably rescue her.

Thanks Salvatore!