I would advise you to do proper research on dry fasting (look up the books from Filonov and Dunning for starters), then decide for yourself what you want out of dry fasting and after that try out protocols from experienced people.
Just casually reducing water intake without making sure to get hydrated through food will most likely just mess up your digestion and get you constipated.
You don’t need to drink water if you are drinking hydrating foods like fruits and vegetables. However, most people’s diets are filled with salt and sugar, so water is pretty important to help flush them from the body. It would depend on what you’re eating as to whether it’s a good idea to not drink water at all and just eat it. If you eat your water, I don’t see why there’d be any issue