I just rediscovered this "trick" if you will, after 10 years of experimenting, I remember now from my days of working out hours on end. However, I don't think one should make a habit of (ab)using carbs in this manner, that good pristine carb rush effect might subside.
And that is exceedingly dangerous for workout motivation. You don't want to become dependent on any routines and habits to complete a workout.