I've been on a daily creatine regimen for a few months and I feel like it has had significant cognitive benefits. I have lifelong insomnia and sleep deprivation, and also ADHD which mostly manifests as very poor motivation (which is hugely effects by how bad my sleep has been).

The research I've seen indicates that creatine is specifically beneficial for improving cognition under sleep deprivation. This is the protocol I've been using: https://brandonluumd.substack.com/p/creatine-for-the-sleep-deprived-brain.

I know its difficult to self assess stuff like this, versus placebo, but becuase my cognitive impairment is so severe when I'm sleeping badly I think the improvement from creatine has been really noticeable for me. I'm a programmer so I have a pretty clear benchmark for cognitive ability on any given day, my ability to think clearly has very obvious impacts on my work. Its been startling to be able to operate at a high level in circumstances I would normally be cognitively crippled and unable to do much of anything.

I would recommend trying it for anyone who has similar issues to myself.