For healthy toddlers experiencing an episode of diarrhea due to a viral illness, a regular age-appropriate diet is best.
Continuing their regular foods will offer the nutrition a child needs to heal their gut. Even milk and milk products are acceptable provided the caregiver does not notice an increase in the frequency of diarrhea.
Avoid juices like apple juice as the natural sugar content of juice can pull even more water into the gut making stools even more watery. Food such as eggs and chicken give valuable protein, and rice and potatoes are nearly always tolerated well. The often touted BRAT diet—bananas, rice, applesauce, toast, and tea diet—is too low in calories and nutrients to be given exclusively. Eating a regular diet will not stop the diarrhea but will maintain a healthier overall state than giving the gut “rest” by feeding only liquids.
Of course, follow your child’s lead, and do not force anything that seems to make them uncomfortable. If the stools are painful, bloody, or accompanied by fever and vomiting that prevents any oral intake, seek medical attention.