Sleep potion doesn't really make sense either, unless you had dozens of them. One potion knocks out 24? HP worth of bad guys, so diluted it should do absolutely nothing to an entire camp full of creatures.
Spiking it with (Lots) of hard alcohol might make sense, but then the "common sense" of trying to combine it with a Barrel of Firewine would be fairly jarring. Maybe if you could just leave a Barrel of it near their current stash, or replacing an "Empty Firewine Barrel" with a full one.
