In co-op, you share a single canteen. Do you drink, or does your friend who is already hallucinating drink? The game tracks "Shared Sacrifice" XP bonuses, which means the community is actually helpful rather than murderous—because killing a teammate wastes their precious bodily fluids. (Yes, that’s a mechanic. Don't ask.)
If for some reason you cannot find the official app (region restrictions or device compatibility), here are three worthy alternatives that mimic the Parched experience: download parched