Talk to Rufus in Goodneighbor's Hotel Rexford for a chance to get a new “job”. If you accept the job, you’ll get this quest. Your objective is to head to Shamrock Taphouse and retrieve the brewing machine there.
There's a raider defensive perimeter around the building. Refer to the location's dedicated page to know what notable items to loot. Your objective is to reach the basement of the establishment where the modified protectron called Drinking Buddy is stored. The terminal to free him is Expert difficulty but you can get the password to unlock it with ease. The password to the terminal is located on top of the shelves, as a holotape on top of some wooden crates under the flashing red light.
After activating Drinking Buddy, you have to deliver it (escort it) to Hotel Roxford or send it to any of your settlements. Take note that the quest won't be completed until you deliver it to Rufus. Also, take note that the protectron itself is quite defenseless and can be destroyed before even reaching Goodneighbor. Make sure to save often and escort it safely back to the hotel.