When a vehicle is created by the server on server start up it loads a variable amount of loot inside of it. This can contain items such as guns, food, medical supplies and/or building materials. To access the inventory of a vehicle such as a car, truck, boat or helicopter, all you need to do is approach the vehicle and press the inventory button (Default 'I'). This will open a menu with four available options. Click on the 'Inspect' button to open the vehicle inventory. Different vehicles can store different amounts of loot inside of them.