Sugar
Sugar is a sweet substance found in many foods that gives your body quick energy.
Think of it this way
Sugar cubes sit in a bowl like small packets of quick energy. Drop one in a glass of water and watch it break apart. Tiny bits spread through the whole glass. Your body does the same — it breaks sugar into small parts your cells burn for fuel.
Explaining sugar by grade level
When you eat a jelly bean, the sweet taste comes from sugar. Your body uses that sugar for quick energy. If you eat too many sweets, your body stores the extra as fat. That is why mice fed jelly beans gain weight fast.