Symbolism, Imagery, Allegory
Henry's depression reaches its height when he starts storing his pee inside Gatorade bottles. He doesn't want to leave Pella's bedroom except to watch TV and do dishes. Even so, he won't leave to pee. He likes saving his pee: "Part of him, the truest Henry-part […] wanted to keep the pee forever. […] He didn't want to rinse out the Gatorade bottle, okay? He wanted a permanent collection of all his pee and s***, not that he ever shat anymore, now that he'd stopped eating" (68.16-68.17). Yeah, we know: eww. Plus he leaves them by the bed, where Pella could accidentally drink out of one. (Would she be able to tell the difference between pee and warm Gatorade? Let's not find out.)
Okay, Henry done lost his mind, y'all. He's become a weirdo hoarder, hoarding bodily fluids because he desperately doesn't want anything to change. Does this strange tendency of his pop up anywhere else, or does it only manifest itself here, when Henry is at his worst?