If you follow a keto diet, you should have at least 2,5 litres/4 pints of water a day!
You can also have tea and coffee with or without milk or cream. We recommend using stevia or monk fruit as sweeteners instead of sugar. Both of them are plant-based and don't contain any calories. Xylitol is among the better choices because it is a dental protectant, and because it provides usable energy.
Also, please try to avoid fizzy drinks and juices. Alcoholic beverages (except for strong ones like vodka and whiskey) are relatively high in carbohydrates, and they should be avoided. A glass of dry white wine can be an excellent choice during dinner.