I think the biggest issue is the quality of the water rather than how the tea is prepared. I generally just boil the water in an electric kettle and pour it in a teapot right away for black tea and cover it with something so that it cools down slower, or in the case of green tea I let the boiled water sit for a few minutes and then pour it in the teapot. Considering I follow pretty much the same procedure both at home and at work, the tea I make at work tastes worse, because the water, even though filtered, just tastes very flat.
By the way, I thought I remember reading something that suggested that tea is supposed to fix, not cause bad breath (by getting rid of the bacteria on the tongue or something like that).