How to lose belly fat in 8 days?

What ? - in 8 days! There isn't such a thing as natural spot fat loss. You need to lose weight in general ; a certain % will be abdominal fat. Eat healthfully ; be physically active. Calories burned must > calories consumed. To tighten ab's do crunches, reverse crunches, exercise ball crunches, pelvic thrusts, lying leg raises, side bridge ; “bicycling” exercise on your back. Engage in regular aerobic exercise.
Avoid refined sugars. Try to avoid refined sugars, alcohol, salt. Drink plenty of water. Exercise. Remember the best recommendation is that slow and steady weight loss is the best for long term success.