Liquid Courage
This section of IGN's Far Cry 6 Wiki Guide details where to find the Liquid Courage Treasure Hunt and what reward you'll get from it.
Reward: 150 XP, Into Orbit Rocket Launcher
Location: Star Rocket Brewery, Noventarmas, Valle de Oro
This Treasure Hunt can be found at the Star Rocket Brewery, which is located in the north of Noventarmas, Valle de Oro, near Del Toro Port. The orange box with the Liquid Courage note is located on a table near the bar inside of the brewery.
Liquid Courage
According to the Liquid Courage note, María Marquessa has plans to take over this brewery but the owner locked himself in his office, refusing to hand it over to her. Apparently, there are valuables stored away with him as well. So, it's time to figure out where his office is.
Unfortunately, the property is locked down fairly tight, and there's no direct way into his office. So, you'll have to find a creative way to get in. If you head through the door on the right past the bar, you'll end up in a larger room holding all of the beer. Up the stairs, you'll also notice a valve with three red lights above it.
In order to get through to his office, you'll have to blow a hole in this joint by turning three different valves that will overpower this main one. The first one is located near the door you came in from. After turning it, head to the opposite side of the room and up the small set of stairs, then turn right and walk straight ahead to find the second on the left.
The third is located above you. So, head all the way up the stairs to the top platform near the open window. Hop over the rail at the end and follow the pipes along the side of the wall up and around to the opposite wall where you'll find the third valve.
Now, jump back down to the main valve and, now that all three lights are green, turn it to blow a hole in the wall above you. Then, grapple up into the hole and take the tunnel on the left through the vents.
Take another left through the vents and then drop through the hole ahead of you. This will lead you into his office. Unfortunately, he's no longer alive, but you can find the Into Orbit Rocket Launcher in the Treasure next to him.