I suggest you don't try to treat diarrhea without consulting a doctor. There are different types of organisms which cause diarrhea, and they just don't go away by drinking lots of tender coconut water or lemon tea. They have to be treated with medications or they only grow in the stomach and intestine and later have to be treated with much stronger medication and for a longer duration.
Here are some food do's and don'ts. Try to avoid milk as far as possible for at least 48 hours. If  your child wants only milk, dilute its strength with clean water. Light tea may also be good. Ideal is to give milk only in the forms of curds or buttermilk for two days. If the child can drink buttermilk replace each milk feed with a glass of buttermilk or lassi. For breakfast,
give bread toast or idli dipped in curd. Salt and sugar may be added to the curd. Avoid rasam and dal at lunch and give only curd rice for lunch and dinner.
The reason for avoiding milk is, it is an ideal medium forbacteria and other organisms to grow on and the infection inside will increase instead of being controlled and destroyed. On the other hand, curds has bacteria which can fight the organisms causing the infection. Therefore, for diarrhoea, curd is a form of natural treatment.
Please avoid eating non-veg completely for atleast 48-72 hours. Non-veg food again is the ideal medium for organisms to grow and you will only see the infection increase rapidly if non-veg is eaten.
Also other food stuffs e.g. arrowroot, apple, tender coconut water etc, cannot kill the viruses or bacteria so they cannot be used as a treatment. However arrowroot porridge, arrowroot biscuits, apple and tender coconut water are soothing to the stomach and help to bind the stool so they help in reducing the frequency of passing motion.
They also help to replace calories, minerals and vitamins, which are lost during diarrhea.
 Apart
from toast, rice and curds, Marie or arrow root biscuits, rusks, apple, black tea with little lime juice and sugar, rice kanji with salt and curds and arrow root porridge and tender coconut water are ideal to be consumed in the first 2-3 days. B complex and C vitamin supplement is very important during diarrhea. Take a capsule or syrup form of this morning and evening.
The biggest danger faced in a diarrhea is dehydration and blood sugar levels dropping. During acute diarrhea, the danger of dehydration is so great that one should not wait but immediately start treatment to replace fluids and electrolytes. Electrol available from a pharmacy may be prepared with boiled and cooled water or oral rehydration may be prepared at home by mixing one glass (200ml) clean water with 2 teaspoons sugar, a pinch (quarter teaspoon) salt and 1-2 teaspoon lemon juice. Pour small portions of this into a separate glass and allow the child to sip this at frequent intervals. | 
