One banana every ~50 km is far too little. That's only about 120 kcal (one banana) every 2 hours (assuming 25 km/h), versus a recommended 200 kcal every hour. You ate only about a quarter of the calories you should aim for. No wonder you were running out of energy!
I like to get some calories from liquid food (chocolate milk, grapefruit juice, etc) and some from solid carbohydrate food such as bananas, bread, homemade energy bars, etc. Half the calories in yogurt are from carbohydrates and that works well for me too.