Need to start antibiotics in your case. Is he running fever as well? In a diabetic patient, causes of diarrhoea can be mamy. History in detail needed to get yo the confirmation.
For now, ypu can start with
Tab Pantoprazole 40 mg before breakfast once daily x 3 days
ORS solution 1 packet in 1 litre water twice /thrice
Give lactobacillus sachet once/twice daily with water.
If more than 4-6 stools, give him tab loperamind 2 mg stat
Then consult online
Keep checking his blood
sugar
If fever or pain abdomen present , consult online urgentlu for prescription.