"have green tea ,coffee ,diet drink ,diet pop whatever. Some gum."
Well, actually all those things may be quite dangerous when you fast. It is the best trying to stay away from them while fasting as your digestive system is at rest and you don't want to poison your body with soft drinks, coffee, etc.
That's OK to drink them when you are not fasting since your liver and kidney are fully functioning and ready to neutralize toxins and poisons from food and drinks.