Don't worry, not an excuse, but definitely an advantage! I plan to eat 3 healthy meals, but no extra snacks on Sunday. It's really hard to go from eating 3 square meals and several snacks to nothing! Space out your meals, too, and go to bed early Sunday evening - nothing worse than a tired-ness headache (on Monday) and no cup of tea! Drink plenty, but no caffeine (don't forget there is caffeine in wine, chocolate and tea, too).
Good Luck, and Godd Yom Tove to you and your family
Our Yom Kippur Fast is 25 hours long - starting at the beginnning of sunset the night before (ie Sunday) and finishes at the end of sunset the following night (Monday). It is not permitted to eat or drink anything during that time and one should devote the day to penance and prayer to G-D. All healthy children and adults over the age of 13 years old should observe the fast.