I am really big on the less treats the better. Chinchillas do best with a very bland unvaried diet. If you want to spoil your chinchilla do it with new wood toys, apple branches, and that sort of thing. Those will keep your chinchilla's teeth healthy, give them longer enjoyment than a treat, and be healthier in the long run.
If you absolutely feel you must give treats stick to something healthy. Rosehips, and Quaker Oats are both good chioces.