I think it's better to have a normal time schedule, at least before the start.
Changing suddenly habits can make more harm than good.
After all, if the competition starts at 2 AM, you can wake up early with a clearer mind.
You will lose some time, but you will make things better and probably faster.
I am no expert tough, just my opinion.
To have a clear mind during the day, try to follow a schedule, like, every hour make a 2 minutes break.