Carrots are one of the better treats you can give a dog. Raw carrots are low in calories, high in fiber, have decent vitamin content, and the crunchy texture is something a lot of dogs genuinely enjoy. Frozen carrots work especially well — they hold up longer as a chew and the cold seems to appeal to dogs, particularly puppies that are teething.
No prep needed beyond cutting to an appropriate size. For small dogs, slice them into coins. For medium or large dogs, a whole baby carrot or a stick of regular carrot works fine. The only real concern is choking if a large carrot chunk goes down too fast — just cut them reasonably.
The teeth benefit is real
Raw carrots have a slightly abrasive texture that can scrape plaque off the surface of teeth as a dog chews them. It's not a substitute for brushing — nothing really is — but as a supplement, it's more useful than most treats. Frozen carrots especially can provide meaningful mechanical cleaning while the dog is busy chewing.
If you're looking for low-calorie treats in general, carrots compete well with blueberries as a go-to. The difference is mainly texture preference — some dogs go for crunch, some prefer something softer and sweeter.
Cooked carrots are fine too
Cooked carrots — plain, no butter or seasoning — are safe and some dogs prefer the softer texture. They lose a bit of their abrasive benefit for teeth when cooked, but nutritionally they're still fine. If you're already cooking carrots for yourself, setting aside a few plain ones for your dog is easy.
This is one of the cleaner "human food for dogs" situations. Nothing to worry about here.