For optimum digestion, fruits should be eaten on an empty stomach and the only time the stomach is truly empty is first thing in the morning.
Fruits digest very quickly and are usually in the small intestine within 30 mins, where they'll continue to digest. Others foods such as protein and starch can take three hours, five hours or even longer to digest. If fruits get held up in amongst this digestion then they will start to ferment. Fermentation can create the perfect environment for yeast overgrowth and also poor absorption of vitamins and minerals.