What can't Jews eat on the sabbath day?

On Passover, leavened foods made from or containing any of the 5 grains (wheat, rye, barley, oats, and spelt) may be eaten, because of the prohibition against leavened foods in Passover (Exodus ch.12). This includes bread, pasta, cakes, pastries, crackers, pancakes, Pizza, cereal, etc.
Instead, unleavened bread, which is called matzah is eaten. Matzah may also be ground into different consistencies to cook with. Other foods such as fruits, vegetables, eggs, meat and fish, are permitted, following the year-round rules of keeping kosher.
Ashkenazi Jews have a custom which also prohibits grains such as rice and corn and legumes such as beans, lentils, and peanuts during Passover. The restriction applies to their use in all forms, so it prohibits the ingestion of products that use corn syrup such as candy or soda and many others. See:

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