Horses love fruits and vegetables, so maybe try giving him apples,carrots,cucumbers one horse at my barn LOVES oranges. You could make your own horse treats without sugar,I know my horse likes homemade ones!Hopefully this helped!
If your pony is not allowed to have sugar, you could try some natural foods (fruits and vegetables) such as apples and carrots. Some types of horse treats are also naturally made and/or have little to no sugar added to them. If you have some time on your hands and want a little project, try making your own horse treats! The internet is a great place to find some recipes :)