Can water be replaced with fruit juice? So instead of drinking a certain amount of water daily, would it be better to get your H2O from fruit juices?
How about veggi juice?
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There's no absolute "better" or "worse" for this type of substitution. It depends entirely on what problem you are trying to solve and what nutritional goals you are trying to achieve.
To answer your question most literally — "Yes", you can satisfy your daily water requirements with fruit juice. There is sufficient water in virtually any fruit juice for your body to extract the water it needs.
But water and fruit juice are not the same thing. Only you can decide what that balance is to achieve your goals (or provide more details in your question to get it answered properly). Consider also: Why the extremes? Why is it all water or all juice? Moderation.
Some differences to consider:
Fruit juice is, essentially, a food. It provides nutrition. It provides calories. You should treat it like any other food; You should know what you are putting in your body and why.
You're supposed to drink 8-10 glasses of water a day. 8-10 glasses of juice is a lot of excess calories and sugar. You might find yourself gaining weight at a rapid pace which maybe you want. It's like drinking soda.
355 mL can of Coca Cola = 39g of sugar
200 mL juice box of Trader Joe's White Grape Juice = 30g of sugar
Just some thoughts to consider if you do switch.