Here is a guide.
Caffeine is the most commonly used drug in the world. It is an addictive stimulant which causes headaches and feelings of anxiety in some people and may bring on withdrawal symptoms, such irritability, headaches and fatigue, when you give up.
Caffeine also makes you urinate frequently so tea, coffee and coke are not good thirst quenchers. Drink lots of water in hot weather or when exercising.
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