You can't give human diarrhea medication to cats. You used to be able to give kaopectate, but the recipe changed recently and that is no longer safe.
You can try mixing some infant rice cereal into some baby food. Make sure the baby food does not have onion or garlic in it. Also feeding a tsp a day of plain yogurt does a good job firming stool. It adds good bacteria to the digestive tract.
Take up cat food and use the baby food/rice cereal mixture for a couple days as his primary diet. This is easy on the stomach and will hopefully help firm things back up.
If the problem continues, then a vet visit is wise.
Yes I meant replace his regular food.
yes you can use boiled chicken, beef, fish, etc. Fresh meats are fine as long as it is boiled as the method of cooking and you use no seasoning. Using fresh meat like chicken would be better since he is diabetic.
I am not 100% sure what is available where you live, but here in the states we have many OTC pet medications to choose from like "HomeoPet Digestive Upsets" and "PetAlive RunnyPoo Relief"
Just ask for what pet stores in your area carry for diarrhea in cats.
Watch what kind of stock you use. Look at the back and make sure there is no onion or garlic powder in it.
As for ginger, I do not believe that is toxic to cats.
You are more than welcome Natsuko :) Let me know how things go and if you need any more help.