Viral fevers sometimes cause diarrhoea. Puff rice will not cause loose stools. You can give hime coconut water, butter milk, curd rice, water,WHO ors solution with appropriate dilution, avoid fruit juices temporarily as it may cause loose stools.
Next Steps
watch for dehydration signs like.sunken eyes, dull activity, decreased oral intake, decreased urine output. if these signs are there reach out doctor immediately