Sugars will crash your system and make you tired.
No carbs at all will keep you lethargic... for a while, then your body will get a bit used to it, and you'll feel clean, but you won't have a massive store of energy.
Playing with carbs is a good learning experience I think. I believe everyone should go on a no carb or very low carb (all carbs) diet for a lil while... feel what it does to them, and how your body reacts when you eat sugars... and how eating complex carbs keeps you stable.
People need to learn to listen to their bodies!