Yes, I would insist you to sleep twice a day. One day  before any exam, have a good nap. After doing any physical work, you need energy. Sleeping is the best way to get energy and refreshnes.  But that doesn't mean that you have to brush thrice. 

Before any program I take a nap. Your skin starts to glow and you get fully refreshed. Sleeping is best for health as it gives the brain refreshnes and energy for the next day.A nap in the afternoon is called power nap. When I  wake up from my  power nap I   feel a  boost of energy and feel confident enough to study. But the following lines are somethings you should avoid while sleeping.

Don't sleep right under the ac. Sleep a bit far.

Dont drink water right before sleeping.

Go to the washroom, then sleep.

Before sleeping in the night, brush you teeth and after waking up in the morning.