Recommend Suitable Medication And Food For A Child With Watery Stools, Vomiting And Severe Stomach Infection While Recovering From Dengue

Hello doctor!!my son is 11 year old and weighs 40kg.he z havingsevere stomach infection and has just recovered from dengue.passes watery stools nd has puked thrice since morning.Rt now he is only on ors.what medicine would you prescribe and in what dosage??.kindly suggest accordingly the food he can have also stomach ache just started