There is a cock desire limit for cum swallowing, you can find it if you've purchased the right "release personal info" edicts.What determines if prisoners cums in the pint glass during the barmaid job? It seems to be random chance. I wonder if there's a way to influence the prisoners to cum in the glass. Trying for some of the titles that require Karryn drink X amount from the glass can be a bit frustrating to get
Once that desire limit is met, the prisoners will dump the beer out and start jizzing in the mug.
Stay below it, though, and you can just keep on drinking beer and receiving tips for it.