credit goes to the guy, i just quote him
You will need two things: Alcohol and a Survivor. Make sure your Survivor has very low health. Otherwise you can't hand over the bottles. Simply let the Zombies damage him / her. Now search for some alcohol, doesn't matter whether it's beer, wine or vodka. Go to a place where no Zombies can interrupt the process. After 2-4 bottles the survivor should puke.