What to eat when suffering from gastroenteritis?

Bland diet. Take it easy and try to have a bland diet - banana, rice, toast, and plenty of fluid.
BRAT Diet. The brat diet is used for diarrhea, dyspepsia, and/or gastroenteritis. It consists of foods that are exceptionally plain and low in fiber. An acronym, brat is a mnemonic for bananas, rice, apple sauce and toast, the staples of the diet. Extensions to the brat diet include bratt (with tea), bratty (with tea and yogurt), and bratch (with chicken, often boiled). Sometimes the "t" represents tapioca.