Exogenous ketones (such as BHB salts) are known to help with glymphatic drainage in the brain during sleep. I've used them extensively and have noticed improved sleep with nearly a doubling of the time spent in REM stage.
Sure. When I have a night of poor sleep or anticipate one, I usually take 6 grams of BHB salts in the morning on an empty stomach. You can work your way up to a maximum of 12 grams, but I would advise caution since it can cause diarrhea. I would start by buying the cheapest product (nutricost) you can find online; if it costs more than $80 for ~300g, then you're probably getting ripped off. I noticed that I have very lucid dreams and experience strong hypnagogic jerks when I take this supplement.
Here is some literature that I've perused to support my experimentation with BHB salts:
