Can we contrast fasting like the op is describing (with coconut milk, protein supplements and bone broth) vs. fasting with literally zero calories ?

If you're pursuing "weight loss" or fat loss or general fitness/wellness/lightness, I think any form of fasting is useful and interesting.

However, it seems to me that if you are optimizing for starving cancer cells, forcing weak cells into apoptosis, depleting your sugar stores, resetting insulin resistance, etc. ... that is to say, if you're pursuing the more interesting, second order benefits of fasting - you really should be doing the zero calorie kind.

I do a 24 hour fast once weekly with just (black) coffee and water ... I guess I cannot speak to how difficult zero calories would be for 2-4 days ...