While fasting, water, unsweetened seltzer, tea, and black coffee are all permitted. Some intermittent fasting practitioners allow small amounts of cream, half-and-half, or milk in coffee. This is fine if you are using intermittent fasting as a way to decrease your overall calorie intake. If you are using intermittent fasting as a way to get into ketosis, keep in mind that even small amounts of caloric liquids may increase your blood sugar and insulin levels.