As a sufferer of IBS I can tell you that apples and other citrus fruit irritate me. I also find that I cannot eat more than 3 portions of fruit and veg per day and that I can eat too much wheat fibre, while beans, pulses, cauliflower and broccoli make me ill.
Each morning I eat porridge with dried fruit including prunes. This gives me a filling breakfast containing two of my three daily fruit and veg. The oats give me a good dose of fibre without irritating me. I would recommend this breakfast to anyone without or without illness.