My Nemo ( 5 months) loves frozen carrots. Also bullies, esp the braided ones. And loves, loves, loves Cow tracheas (gross I know) but he loves them. I get my bullies and trachea at organicbullies.com. Use code "healthydog" for $5.00 off your first order. They are quick to ship products also.
I buy 5 pounds of carrots at t time. Wash them, cut them up and put them in ziplock bags. 2 of my dogs are allergic to grains, 1 to chicken. I give carrots as treats instead of commercial treats. Good for the teeth, no allergy problems, no mess, easy to find at any grocery store.