A Cutting Powder box can be found at the eastern storage area at the fields. It can be used to contaminate the island's water supply by throwing the powder inside the water tower, which will weaken the guards and make their aim less accurate during The Cayo Perico Heist.
Points of Interest
On a shelf in a small building.
On the ground under a small shed at the Crop Fields.
GTA V exclusive locations | GTA Online exclusive locations * denotes roads that are also marked as neighborhoods in the HUD. † denotes neighborhoods in which their names are not displayed on the HUD, but are mentioned on the official map.