Where
A Wild Wasteland encounter is placed north-east of the Crimson Caravan Company, by the Mole rat ranch.
The note
There is a note on the table, which reads:
Yellow Nuka-Cola
Yellow Nuka-Cola is a joke item, based on the item found in Fallout: Tactics. It acts as a poison which lightly damages enemies and causes any attacks dealt to them to crit. Like any other poison in the game, you can apply it to melee weapons. Like other poisons in Tale of Two Wastelands, it can even be applied to darts.
As you can probably guess, it’s just a bottle of piss.