Caffeine is also available for fasting. Caffeine can be incorporated into most liquid fasts including coffee or tea. Black coffee provides a common source of caffeine that is known for boosting cognitive function and reducing inflammation.
It is wise to consume no more caffeine than recommended by the FDA; 400 mg daily. Overexertion of this limit could lead to headaches, insomnia, depression, anxiety, and irritability. It's a great alternative because many products are sugar-free and calories-free and both.
You can read here about the best high caffeine energy drinks that are 100% safe for your health.