Sugar doesn't have the concentration of minerals that molasses does........it does have carbohydrates though. You won't get the same effects that you would from molasses, but it won't hurt either.
If you use beneficial bacteria in your soil they don't care where the carbs come from - I have seen no research on quantities so go slow. I am talking about the veg stage here - just so nobody misunderstands. As far as using sugar for the flowering stage - ? IDK but could there be a reason the pros use the molasses instead? I honestly cant give you an answer but if it isn't broke don't fix it.