It’s completely safe to dry fast for a week or so, after two days your body starts creating an endogenous water from your fat stores and damaged cells, so you aren’t at the risk of dehydration and you won’t feel thirsty.
Recommended by… Muslims? This is the Ramadan schedule and they intermittent dry fast during the day for this period.
Check out the Russian doctor everyone keeps referencing if you’re interested in health/weightloss/non-religious benefits