Hi Guess by now, you would have consulted a doctor. Coke or carbonated beverages are not good for kids and not good at all to be given during diarrhea/vomiting. It will increase the gastritis and increase the frequency of loose stools. Give him plenty of curd, water, vegetable soups, soya milk, rice based porridge, mashed potato, banana etc. Avoid fruit juice, cow`s milk. You have to be cautious as in a kid with diarrhea and vomiting, cold limbs may indicate dehydration. How ever there are other things to diagnose dehydration like dry mouth, dry skin, less urine output etc. I would suggest that you see your Pediatrician. If his activity is less too, its a must that you see your Pediatrician. Hope my answer helps you. Wish a speedy recovery for your kid.