What percentage of daily carbohydrates should come from sugar?

Most of your carbohydrates should come from complex carbs, not simple. The latter is absorbed fast, giving you short term energy, where as complex carbs give you long lasting energy and will help you feel full. Foods such as oatmeal, vegetables, and grains will give you the energy you need. Keep in mind sugar releases chemicals that promote fat storage. When you are eating sugar, try to make it after a workout as this is when it is most useful to your body, and in a perfect world all of your sugar intake should come from fruits and veggies, and other natural foods such as milk. I hope this helps you and please not I am not a doctor and you should consult your Doctor for your own needs.