Anything with calories in it is off limits, because it will break your fast. This includes all soda and juices. The only exception to this rule is if you’re following a controlled fast, such as in the Warrior Diet or the 5:2 Diet, where fresh fruit and vegetable juices are permitted in moderation.
What you shouldn’t drink when fasting includes the following:
Alcohol: Alcohol is quite calorically dense, so stay away from it.
Any diet beverages: They include soda, tea, and other similar drinks that contain artificial sweeteners, including aspartame, Splenda, and stevia.
Juice: During a strict fast (such as intermittent fasting), juicing isn’t allowed. But if you’re following a controlled fast, such as the 5:2 Diet or the Warrior Diet, then fresh vegetable and fruit juices are allowed, such as carrot and ginger juice.
Sugar- and/or cream-laden coffee or tea: Anything with calories in it will tax your digestive system and sabotage a strict fast. Avoid any such additives to your coffee or tea.