Hermione -Right now (the whole day) you should drink a few bottles of Pedialyte. If you’re feeling better by tonite you can fast. If not continue with the small amounts of Pedialyte. If you vomit up the liquid Pedialyte start with the frozen Pedialyte. Don’t eat solids until your stomach is settled usually after it stops (N/V/D) about 24 hours.
PS. – My free medical Chessed for Erev Yom Kippur.