dd is breast fed but when trying to find out if she needed milk in the night we offered her slightly sugared wtaer in a bottle (the sugar just makes the water taste sweet like milk - formula or breast), she was taking a little bit but not much and then going back to sleep till the morning, when she woke in the morning she was ready for a feed but not starving, so it stood to reason that she didn't really need night time milk, we did this for about a week or so and she got out of the habit of waking.
hope this helps.