Fasting✨

Ta
I'd like to know how any of you fast for a week+? I want to start spiritual fasting for clarity, purification and my meditations but I've never successfully made it a week without caving into food.
I'd preferably like to do a liquid fast, 
for example:
soups, shakes, smoothies, water and whatnot so I'm not completely taking everything from my body but I'm open to suggestions. 
I'm pagan but there aren't set ways that I could find for pagan fasting so I'd like to know how any of you do it.
I don't want any negativity or people trying to discourage me, I know the risks and I'm ok to do this with confirmation with my doctor.