Pasta, pasta, and more pasta (especially with it being the Nine Days). Whole wheat pasta is particularly nutritious, but plain old spaghetti or macaroni will do it, too.
Power-Ade is a GREAT way to prepare for a fast. I was taught this tip by someone last year. Don’t be afraid to drink lots of water all day tomorrow. ease up on even decaf, but especially stay away from all caffeine including coffee, tea,colas, and chocolate> Caffeine is a diuretic.
May everyone have a most meaningful fast, unless Hashem at the eleventh hour turns this Tisha B’Av into a yom tov.