during the fast that have to be kept. And yes, you can eat and drink anything during those hours mentioned, but then, after fasting a whole day, it becomes difficult to eat anything too heavy also. The body metabolism will get affected and you may not get good sleep. So, it's very important to eat the "right" food and in the right amount so as to remain healthy, alert and not get dehydrated either. It is quite a challenge. Fruits, vegetables, and lots of liquid in the form of water or juice is recommended to replenish your lost energy. It's very difficult to eat "all" the groups of food in one meal, although it would be desirable.