When you drink to thirst on your Water Fast your body gets the rest of the water located in the fat, so when it is autolyzed it fuels the body during the fast. When you start refeeding and eating other things besides high water content fruit/veggies ... your body is going to absorb and store what was lost during the fast.
For my body type ... I retain salt. I learned through my many fasts if I refeed on other foods that are not high water content my body literally bloats and becomes highly dehydrated. I had to drink 5-6 liters of water on one day just to quench my thirst ... it was 3 days after a fast and I thought bread would be good for me. Nope ... it sent my body into a tailspin. I bloated ... I couldn't quench my thirst ... I got cramps ... it was awful.
I discovered after making this mistake that my refeeding need more time with just high water content fruits/veggies. So if I do a 10 day fast I spend the next 30 days usually on fruit and veggies. Otherwise I seem to not recover well after the fast.
We don't know what happened inside our body ... we don't know what was actually autolyzed or where exactly our electrolyte balance is when we end our fast. I suspect for my body I must have a lot of sodium just lingering around and this is why I don't do well refeeding on other foods. I just started a fast and this one will be longer. I plan to finish at the end of June and then spend the rest of the summer doing nothing but visiting fresh fruit/veggie stands to eat. I will do an entire 2 months on raw. It is kind of my little experiment. I tell people I am salt intolerant because salt wrecks havoc on my body especially after a fast.