Japanese Green tea is the most bitter tea, I ever tried and got addicted to. Its good for everything and good addicted peoples. Chinese olong tea is also equally good, but, you can not drink the amount you can drink green tea. Well, coffiee is not replacement to tea, neither vice versa is true. I suggest you drink tea coffiee without sugar, you will find the advantage of drinking tea coffiee without milk without sugar: i.e. you can drink hot coffiee turned to cold too for whole day, the taste is not lost. But, if its milk tea / coffiee, then, after certain temperature drop in the liquid, its worst in taste. GP