A friend of a friend was recently telling me that she had spent three days eating nothing at all and just drinking water. She was doing it to lose weight and said it was a great way of doing it.
I sort of 'hmmm'ed and came away thinking it sounded unhealthy both physically and mentally.
I once did the 24 hour sponsored fast as a teen and by the end of that I felt ropey and dizzy. I'm not sure I could manage three days and work too!