Not sure how scientific this is, but the Russian doctors who have been doing this since the 70s have some information in this website that detail how to end a dry fast and also how long to refeed before beginning another dry fast.
From their website:>•The length of the exit period should be twice the duration of abstinence from food and water.
>•Do not start a new fast until you complete the exit from the previous fast.
They have more information on the exit but say the “exit period” is just as important as the fast. So if I understand this correctly, if you fast for two days your “exit period” should be at least four days.
Once I’m done with this fast I’m hoping to get onto a 5:2 dry fasting schedule, so dry fast 2 days then have an exit period and one feasting day before beginning a 2 day dry fast.