Coconut

Water first and food second. The game text says a coconut restores hydration and that the flesh yields a modest amount of calories, so it fixes thirst properly and only takes the edge off hunger.

It shines on a fresh spawn among the palms. No small water bottle yet, the sea next to you is salt and the river is somewhere behind the hills. A couple of coconuts keep you going while you hit stone and wood for the first base. Twenty fit in one slot, double what apples and most found snacks allow, so a pocketful travels well.

It plays the role cactus flesh plays in the desert: water you carry without a container. Once you own a bottle and a base near fresh water, it slides back down the food list and becomes something you eat when it happens to be in your hand.