I believe you are on the Norwegian Sea? They will serve juice in the buffet in the morning (I see a lot of people filliing up for the day) but not during the day. They will sell bottled water on the ship. You can bring both juice and bottled water on board, but bring them individually and not in a case. Also, you can buy bottled water in all the ports you are visiting, if you want.
Have a great cruise.