Why do we get instant energy from glucose?
Because it easily breaks down in the cell with the help of oxygen which provides instant energy to the organism. Glucose does not need digestion, it is directly absorbed into the blood.
Glucose is a simple sugar. Carbohydrates, when consumed, have to be digested into glucose. As glucose can be easily absorbed in blood, it provides energy to the body. Hence, when glucose is directly taken, it does not have to be digested and thus acts as an instant source of energy.