The old advice to starve diarrhea is dead - the gut heals faster when fed. The modern diarrhea diet is light, frequent and surprisingly traditional.

During the active days

Fluids first, always: ORS after every stool, plus coconut water, nimbu-pani, soups, dal water
The foods that agree: khichdi (soft, with a little ghee), curd-rice, dal-rice, banana, toast, plain poha, idli - small portions, often
Curd and chhach: genuinely useful - the probiotics and the ease; most people tolerate curd even when milk briefly misbehaves
The traditional BRAT logic (banana, rice, applesauce, toast) maps neatly onto the Indian plate: kela, chawal, seb, toast - add dal for protein

What to skip for now

Milk for a few days if it clearly worsens things (temporary lactose intolerance is common) - curd and chhach usually stay fine
Fried, greasy and very spicy food - the gut lining is inflamed, not hungry for pakoras
Sugary juices, soft drinks and very sweet sharbat: excess sugar pulls water INTO the gut and worsens the diarrhea
Alcohol and excess caffeine
High-fibre roughage briefly: salads, whole bran - reintroduce as stools firm