A strange new product has come onto the market at the same time that someone has bought up the stocks of beer and grain.
The new brew has wonderful effect but its flavor is odd and ends with a very deep sleep. It’s cheap and widely available.
Turns out that some mind flayers or other psionic beast have been producing and distributing a concoction made from their own milk/extract.
The effects and deep sleep makes people easy and reusable prey.