It's unclear which category the coin belongs to. It is an object without a hitbox but it can be collected by touching it. Bringing a coin to the goal will award the player with extra points. Coin points are added even when all the players make it to the goal. As long as it is not collected, a coin will keep returning to it's original position after every round.
It is advised to put coins in dangerous locations in order to kill other players trying to get it.