The amount of fluid intake you need depends on how active you are and the climate you live in warm or cold.
An unsweetened fruit juice serving can count as one of your five portions of fruit and vegetables a day no matter how much you drink. Ideally limit the amount of fruit juice to no more than 150ml or a small glass. If you do opt form two glasses of juice ensure that there is an interval of at least 4-5 hours between them.
Always check the label so you are aware of what you are buying for example - opt for 100% pure fruit juices that are unsweetened basically means there is no added sugar in it.
Natural juice or juiced freshly made is healthier than the processed ones.