If you drank ten cans of regular Coke a day, that would be 1,390 calories a day.
If you drank ten cans of Diet Coke a day that would be less than ten calories a day.
If you alternated the cans or mixed them together half and half, you would drink the same amount of liquid in a day but consume no more than 700 calories.
By diluting the orange juice with water, the calories will be reduced as long as the daily amount of liquid consumed is not increased.