No sugar is the main thing, as well as starches. The solution they inject is sugar based with radioactive tracers. The sugar highlights any cancer spots in your body that may be there so having no sugar the day before is key as that will interfere with the scan. Your blood sugar level will be tested before the injection. So if you can drink high protein, sugar free smoothies or milk shakes, soups with meat put through the blender, sugar free ice cream, will help.