Order a Macbeth Whisky Shot, and shortly after drinking it you'll collapse and completely black out on the floor. You need to hit up either the main casino bar or the one in your Penthouse suite (if you've purchased that upgrade) – the Penthouse bar is the easier option here, as you can quickly sprint back to it after completing the next step. The method for accessing this secret GTA Online casino mission is very similar to how to get the Kifflom t-shirt in GTA Online, except you do it in the casino rather than a nightclub.
