I posted this in another thread today: https://www.amazon.com/Fasting-Salts-Intermittent-Flavourings-Sweeteners/dp/B07Z55FLJC
The big 3 are sodium, potassium and magnesium:
https://www.reddit.com/r/fasting/wiki/fasting_in_a_nutshell/you_need_electrolytes/
I'm lazy and don't do extended fasts that often, so I use this:
https://www.amazon.com/dp/B07Z55FLJC?psc=1&ref=ppx_yo2ov_dt_b_product_details
I've been using this. I've always slept shit when trying to fast but using this stuff I slept a lot better than I expected