I’m on day 4 of 7 today. I do these usually three to four times per year. The keys for me are: potassium and magnesium supplements and chewing on Himalayan salt throughout the day usually about a teaspoon worth. If I need more salt I’ll dissolve a tsp chicken bouillon into a coffee cup with hot water. That also helps so I can enjoy something at dinner during family time.
Just finished a 6 day fast and restarting doing 6 day on 1 day off for 2 months or until I reach my goal. I bought some electrolytes off Amazon that was sugar free also drank Gatorade zero which has electrolytes but I mostly drank to have something that had flavor. I also bought Glucomannan fiber powder as the first couple of days are tough I drank chicken broth with added fiber to help stimulate fullness (but idk how strict you want to be)