To find out how many ounces Daniela drank on Sunday, we need to subtract the total amount of water consumed in the week from the sum of the amounts consumed from Monday to Saturday.
381 oz - (64 + 50 + 60 + 54 + 39 + 66) = 381 - 333 = 48 oz.
Therefore, the Sunday bar on her graph should be 48 oz tall.