Just eat normally! Eat something similar every WI day so that your weight is consistent, i work on WI day so always have an apple and cereal for breakfast, then a mugshot with chicken followed by a yoghurt and strawberries for lunch, i only drink 1.5 litres of water too and make sure don't eat or drink anything after 1:30pm.
That way my stomachs as empty as it can be by WI at 6ish without me having to starve all day.