This one can be achieved in chapter 3 zone 2. From the start duck and go straight forward under the desk and through 2 holes. Take a right after the pillar and go through a window on the left and drop down turning to the right going down the stairs. There will be a sleeping guard straight ahead standing next to a sacrificial bowl..i would call it that at least. Just vomit into/ poison it by pressing
and the cheevo should be yours.
Adding a short gameclip though there might be some.vids out there on youtube