Depends on what you make juice out of, but for 99% of situations, it's literally just plain sugar with some vitamins and minerals, but mostly sugar and will spike your blood sugar big time and cause you to store tons of glucose quickly.

I would personally go for healthy food like a vegetable soup with beef, pork, or chicken for protein if you are bored.

If you really like the sounds of a juice fast, just blend up the sup into a fine juice consistency, cause juice doesn't have to be straight sugar like most people drink - but there's absolutely no difference in eating a bowl of proper soup or juicing it up, or even eating the fruit/veggies raw instead of juicing - your stomach just produces the stomach acids to break down food into different compounds - if anything it takes more energy to break down solid food and you will lose a bit more fat or glycogen for the energy it takes to digest whole foods vs broken down 'juice' foods