Buck & Eddie end up somewhere cold (the mountains??? idk) & one of them ends up plunging into icy waters. They retreat to an isolated cabin, maybe there's a blizzard, no central heating & it's FREEZING, and they have to strip down/share body heat to save whichever one is hypothermic (maybe Buck?) and, well, it's not enough so they gotta fuck (for body heat) or die.
Buddie Fuck-or-Die/Hypothermia/body heat sharing