Ann Joubert from South Africa came up with this question. Here is Dr. Lekutat's answer via video.
Dr. Lekutat's answer:
First of all, you should drink regularly throughout the day, not all at once. Adults should drink at least one-and-a-half liters daily, unless of course you've been advised otherwise by your doctor. For instance, people who suffer from certain heart or kidney problems mustn't drink too much. Many people complain that often they're simply not thirsty. This is a problem that affects older people in particular. Here are a few tricks that can help: In the morning, fill up bottles or glasses and drink them over the course of the day. Set a timer or use the reminder function on your smartphone to remind you that it's time to drink something. And it doesn't always have to be water. Some fruits and vegetables -- like melon and cucumber -- contain a lot of water and count towards your daily requirement.