The European Food Safety Authority and many others recommend that women should drink about 1.6 litres of fluid and men should drink about 2.0 litres of fluid per day. That's about eight glasses of 200ml each for a woman, and 10 glasses of 200ml each for a man. However, the amount a person needs to drink to avoid getting dehydrated will vary depending on a range of factors, including their size, the temperature and how active they are. So, for example, if you're exercising hard in hot weather you'll need to drink more.
All drinks count, including hot drinks such as tea and coffee, but water, milk and fruit juices are the healthiest. It is best to avoid alcoholic drinks.
Also, try to avoid sugary, soft and fizzy drinks that can be high in added sugars. These can be high in calories and bad for teeth.