I don’t know why you didn’t like his/her (sorry) comment? It is true. Juice is actually really bad for you as it’s full off sugar and very fattening. You could substitute ready made juices to fresh ones but that still doesn’t replace water. I don’t think there is an substitute.
Try your best to drink more as its so good for you and does wonders for your skin 
I drink 3 litres a day!