PLEASE SUPPLEMENT MAGNESIUM. Oh and for other general electrolytes, there are some drink mixes out there with them. Low carb body armor is also an option. I understand that these aren’t options if you are strictly sticking to only water though.
Upon doing research, I settled on going with the ones from LMNT (www.LMNT.com). All other brands I looked into had sugar which I wanted to stay away from. Go for their starter pack to see which flavors you might like best.
Personally I buy an electrolyte solution made by a company called Key Nutriets on Amazon. I drink the solution twice a day. I have been rather faithful with it during my current fast day 21/23 and I’ve had 2 episodes of cramping. This is way fewer than any previous fast I’ve done and this is by far my longest fast yet.