If you drink enough fluid then you will be less at risk of infections such as cystitis and it can lower blood pressure too. You’ll probably feel better and be able to concentrate and perform well.
Most of our fluid intake comes from drinks such as tea, coffee, water, squash, fruit juice and milk. Many people incorrectly believe that our fluid requirements (2.5litres for men and 2litres for women) should all come from water but it is only alcohol that does not count, all non-alcoholic drinks hydrate. Getting the balance right is a good idea for your weight though; some drinks such as smoothies and soft drinks have very high levels of sugar and calories.
So, put the kettle on, enjoy that cup of tea/ coffee or herbal tea but try to avoid the biscuits and cake that go so well with your brew!