That would be feeding and not fasting, and where other deficiencies may easily arise not catered for by supplementing with electrolytes (Vitamins and EFA's for example).
Scurvy will develop on a very restricted diet, but never does on a water-only-fast, so drinking smart water will produce deficiencies because it is essentially a starvation diet if you go ahead with it.
40 to 45 days is considered to be the max' safe time to fast on water-only, and irrespective of any fat deposits. After that, a plant-based diet will do the rest................... http://www.drfuhrman.com/disease/default.aspx