Heat the oven to 180°C. Line a small (22x22cm) baking tin.
Blend the bananas, prunes and walnuts in a food processor. Add the cinnamon, ⅔ of the oats and the oil. Blitz until you get a rough mixture. Stir in the coconut and remaining oats (don’t blitz). Add enough apple juice or extra oats until you get a thick batter, but not a hard dough.
Transfer the mixture to the tin, spreading it out evenly, then bake for 25 minutes.
Leave it to cool in the tin for 10 minutes, then transfer it to a wire rack and let it cool completely.
Cut it into bars or squares.
Store the slices in a cake tin.