It's really up to your body.
Some people just do it on weekends. Some do 40 days.. Some incorporate teas some just water. It's dangerous if you don't take vitamins and get electrolytes in your body..
It's prob better to start with juice or something lite. Going cold turkey is tough. How much do you want to lose? What kinds of things are you eating now?
The fast is more like something that you taylor to yourself. Just doing water you also lose muscle and the heart is a muscle.
Nice ta meet ya
Nik