Some people are concerned about vomiting all of the SN drink and failing. They find comfort going through a two day process to prepare them mentally for the event. Fasting is strongly recommended. Some people have medical conditions that mean fasting has a negative effect on them. Sources say that 8 hours is needed. I would suggest individuals know their own metabolism better than a book. If you know that your stomach feels empty after 4 hours, then I suggest you have a 4 hour fast. Try to avoid eating anything large and heavy. Avoid drinking anything two hours prior to drinking the SN. If you need to, then just plain water. - from stans guide