Too many blood sugar increases can alter the blood PH I believe and increase diabetes risk, so it's important not to have massive blood sugar spikes and eat too much
However it depends on what sort of fruits anyway and how much.
Firstly it depends on the glycaemic index of the foods and secondly the glycaemic load, which is based on the index and carbohydrate quantity consumed.
Glycaemic index foods are based on 3 things.
55 or less is low, 56-69 moderate and 70+ is high.
Load is based on 0.1 - 14.99 is low, 15-19.99 is moderate and 20+ is high.
Having an elevation of slightly over 20 on an infrequent or semi-regular basis, should not be bad in most cases and especially when blood sugar is below normal after exercise or waking, but if the spike was too big I:E: 30%+ on a frequent basis, then I believe that could cause glucose problems and increase diabetes risk through insulin resistance.