Wow… Literally nobody has mentioned the easiest solution? Get enough sleep and use a regular bedtime?
Just getting “enough” sleep for a few nights isn’t going to work. You need to go to bed at the same time every night and get enough restful sleep for months so your body is on a schedule. Then you won’t be tired during the day.
If you are, you may not be getting restful sleep and you need to investigate that.
For me, it was a CPAP. I’m physically fit, normal weight, healthy otherwise, but I was having obstructive sleep apnea. Getting a CPAP was a night and day difference, as my sleep is much more restful and restorative.