I have two corgis who love apples slices, carrots and frozen green beens. Both are excellent treats for dogs that have weight problems.
Other than that, I won't give them table food. We have a vet that made it clear they shouldn't eat the same thing we do. The only reason I let them have the apples, carrots and green beans is because the breeder we bought the youngest dog from told us it would help control his weight.
If you're not familiar with corgis, they can quickly put on the pounds.