Please don't feed chinchillas fresh fruits or veggies of any kind. It can be deadly for them.
Chinchillas should be fed a very bland diet of high quality chinchilla pellets and loose timothy hay. That is all they need and that will ensure they will live the longest.
Chinchillas have very sensitive digestive systems compared to most animals, and compared to other rodents like guinea pigs which are known for being sensitive to changes in their diet. I recommend that treats not be fed to them and if any treats are used it should be for training purposes only and given in negligible quantities (less than 2 pea size servings for the whole day of items that are proven to be safe). The fact is these animals do not need anything but a good dose of affection and peaceful daily interaction.
Added:
Chinchilla diets are something that must be carefully selected. There are many diets marketed to pet chinchillas that have been proven to be toxic. A properly cared for chin will live 10-15 years. Diets with mixtures in them, nuts, fruits, or vegetables besides hay or soy are very harmful. The best pelleted diet is going to be alfalfa based and plain. Loose hay is to be considered the bulk of their diet.