Sap is a useful resource in Grounded. You can use it to make a variety of tools and pieces of furniture, healing items, and armor. It’s a natural resource you can find in the game, but it does take a bit of looking around. Most of it is hidden when you first start the game, but as you progress further into Grounded and create more robust weapons and armor, it’s much easier to find.
You want to investigate any twig or fallen branch in the game. Sometimes, the sap is right next to a twig on the ground, or you can find it still embedded in the twig when you approach it. It won’t be for every small twig you find. Mostly, you want to look at the larger ones that are about the size of a log. When you approach it, you should see a solid orange dot in the wood. All you have to do is approach it to pick it up, and you can find it in your inventory.
Later in the game, you can find much larger sap deposits closer to the base oak tree called sap clumps. Because of their larger size, you do need to use a pebblet hammer to remove them, and when you do, it scatters several sap droplets nearby, yielding four to six per deposit. These locations are a bit more dangerous, so don’t worry about venturing to them until you’re prepared. You can also acquire sap by learning how to make a sap catcher by buying an acorn top and ant mandibles.