Syuba Oil is a Companion drink (most likely alcoholic), also used as currency in the Slums. In most locations of the game you can see Syuba bottles in the trash, on tables, on roofs and on the ground.
The announcement in the Slums says that the Guardian is looking for someone capable of monitoring the southern entrance to The SafeZone with remuneration of two pints of Syuba oil per day.
It can be seen that bottles of the Syuba oil are lying around Stuplachee while he sleeps in the bar, and they also need to be dropped on his head to wake him up.
Syuba Oil bottles in the Slums
Stuplachee sleeps next to oil bottles