Two days later, Group D gets a new boy named Brian, though X-Ray calls him Twitch. Twitch explains that he was arrested for stealing a car. As Twitch talks, Stanley lies on his cot and wonders if it actually no longer smells or if he's just used to it. He wonders if Zero might still be alive and thinks that he's most worried that it's maybe not too late—Zero could somehow still be alive in the desert, looking for water.
Here, Stanley's private musings about his cot serve as a symbolic representation of the way the camp normalizes toxic behavior, relationships, and situations. It reinforces that at Camp Green Lake, toxicity becomes a part of the background, just as the smell of the cot does.
The next morning, when the water truck arrives, Stanley wonders if it's not too late to save Zero. He watches Mr. Sir fill canteens and wonders if he left the keys to the water truck in the ignition. Carefully, Stanley steps around and observes that the keys are right there. He takes a deep breath and reasons that driving can't be that hard. Quickly, Stanley climbs into the cab, starts the truck, and steps on the gas pedal. The truck doesn't move, and Twitch yells for Stanley to put it in gear. Stanley does and the truck jumps forward. Stanley picks up speed until suddenly, the truck bounces and the airbag inflates. He realizes he drove into a hole and reasons he can't even blame his no-good-dirty-rotten-pig-stealing-great-great-grandfather for this. Stanley abandons the truck and runs into the desert with his empty canteen.
It's notable that Twitch is the one to offer Stanley help in this situation; this is his first day, which suggests that Twitch probably isn't so acclimated to the toxicity of Camp Green Lake's culture yet. As a result, he's more willing to help someone else out than the other boys are. Stanley's decision to go out after Zero at all shows that he's decided to reaffirm his belief in the power of kindness and friendship, as he recognizes that Zero can't survive out there by himself. Note too that at this point, Stanley still sees the natural world as being against him, given his lack of water.