A lot of people feel like shit on day 4+ on a water fast. By replenishing your system with electrolytes you can keep your energy levels up and go further in your fast. “Snake juice” is basic salts and minerals in water. If you want variety you can drink homemade Keto Aid or buy something like LMNT pre made packets.
With water fasting you piss out your salts and minerals and are not replaced.
With Snake Juice fasting, you replenish your salts and minerals daily by drinking your allotted amount of SJ first, then drinking fresh water as thirst demands.
For me, SJ is definitely more easy way to fast than fresh water only, I don’t get tired like on fresh water only.