Sugar free yogurt
Mealworms either crushed for easier eating or not, it doesn’t matter really
Clover (mine loved “clover chips” which was dried clover. They wouldn’t eat it any other way!)
Veggies (NOT potato, it’s poisonous to chickens) cut up small
Hard boiled eggs or raw egg in a little container (such as a lid)
You can find chick sticks which are for chicks who peck each other or are bored, but they can still make delicious treats, there are also little squares of mealworms, seeds, and other goodies that are for adults but chicks can love them too! My chicks would do anything for them and would fly up onto my deck and search for them, and eat an entire block.
Make sure before feeding your chicks anything, you make sure it’s in fairly small pieces, and check before you feed them that they can have it. Even things that are in the same jar/mixed in with potatoes can poison your chicks. They can have sweet potato however, but not the white kind.