actually drinking water isn't as good as you think. its good to drink in the sense you aren't adding anything to your body, but you really aren't staying hydrated. water has no nutrients to it at all. its good to drink water but its good to get other types of drinks too like gatorade or something that actually replenishes your body. and not eating is not healthy at all. you have to and need to eat
if you are fasting and relying on God's strengthk, then yeah, def. our bodies are actually made to function best with regular fasting, but if you are just starving yourself, then it isnt really a good idea. if you go one day without food, you will be fine, but i dont reccomend it as a regular habit.
No you still need to get your nutrients in.Water has no nutrients unless it is vitamin water but that is even no good.Sometimes they do this for surgeries and stuff but don't do it yourself.
Drinking water is healthy, but you do need to eat as well. Food provides nutrients that water does not provide on it's own. So no, consuming only water alone is NOT healthy.
*vitamin water is fine just not enough nutrients.