Both coffee and tea contain dehydrated ingredients (caffeine and theophylline), which will stimulate the central nervous system and have a strong diuretic effect on the kidneys. Take coffee for example. If you drink 6 cups of coffee every day, you will have 12 grams of caffeine. To metabolize these caffeine, the body needs to excrete 500 ~ 1000 ml of water. So coffee and tea can not only replace water, but also add more water when drinking these drinks. In addition, coffee has an exciting effect, and people will not feel thirsty even if they are short of water. Day after day, chronic dehydration may occur. Therefore, drinking coffee in moderation and supplementing the water lost by drinking coffee are beneficial to health.

It should have little to do with exam nervousness. Because you are short of water, drinking tea and coffee can replenish water.

And because you drink it often, you will be dehydrated over time.