Yoku's Island Express

There are a total of 25 treasure chests in the game, scattered throughout the open world. Each chest contains either fruit or an upgrade, so it's worth grabbing each chest as you find them. You'll likely find a decent amount of these just from natural exploration as you progress. There is a vendor near the center of the map that sells a map which displays all treasure chests on your map. If you prefer to save the fruit for spending somewhere else, or are having difficulty pinning a chest down, there is a nice map at IGN found HERE that displays the entire map with all chests labeled. Simply open all 25 to unlock this achievement.