What is really the difference?
Dry fasting is very hard because you are also dealing with some amount of dehydration. This sort of fasting is practiced for religious reasons most often. Water fasting offers all the benefits of fasting without the dehydration so it is medically recommended over dry fasting. There is no medical benefit for dry fasting.
This might get lost below, but this paper is quite interesting:
“Dry Fasting Physiology: Responses to Hypovolemia and Hypertonicity”
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Full text here:
https://www.karger.com/Article/FullText/505201
For your question, what is the difference, they have a decent definition:
“Fasting is defined as the voluntary abstinence from solid food and stimulants (caffeine, nicotine, alcohol, beverages) for a limited period of time, while the intake of “sufficient” quantities of herbal tea and water is obligatory [1].
Dry fasting (DF), also called food and water deprivation [2], is defined as the abstinence from any food or hydration”