Best things that improved my performance are: sleep, Vitamin D, and B complex. The most important is sleep

Anything else doesn’t seem to help much.

Sacrificing sleep time will affect your cognitive performance and increase risk for a lot of diseases. “There simply isn’t time” is usually an excuse used when you have poor time management skills, you can try an exercise of writing down what activity you have done each hour segment. This will allow you to be mindful on which activities are wasting your time.

Polyphasic sleep schedules are also not recommended, Huberman has a good episode on sleep w/ Matthew Walker: https://youtu.be/gbQFSMayJxk