Keep these treats to a very small amount and not daily.I give them suitable kitchen scraps (berries, veggies), a sunflower raisin snack mix (Flock Party) from time to time, and I let them graze the yard a couple days a week.
The more treats you give the less of the complete/balanced diet they eat.
Too many treats can lead to over weight birds...over weight birds are prone to serious problems.
Over weight birds are more likely to have reproductive issues.