You have to add the sugar pre ferment or as the ferment is going on. Might have to add more fruit flavor(jam) to help cover the hotter alcohol taste. Use your hydrometer and don't bring the sugar content of the must over about 1.085, will give you about 11% alcohol or so. More will probably taste alcohol hot and hide the fruit taste. Also, make sure you use nutrient, add about half at the beginning of the ferment and the rest when it gets down around 1.060 or so. Arne.