Peel and cut the banana and core and slice the apple. Place the bananas slices, apple slices and strawberries in separate piles on a serving plate. Sprinkle the banana and apple slices with the orange juice and toss gently. Cover the fruit with plastic wrap and refrigerate while you make the fondue.
In a medium saucepan whisk together the cocoa powder and sugar. Gradually pour in the evaporated milk and whisk well to make a paste. Place the saucepan over a low heat and cook, stirring constantly, until simmering. Remove from the heat and whisk in the vanilla and chocolate and stir until the chocolate is melted. The mixture will thicken as it cools slightly. Transfer chocolate to a fondue pot, and keep warm. Serve with cut fruit for dipping.