Crunchtastics are a crunchy candy mentioned in Stellarlune. They are stored in blue-striped bags, and are described by Tam as "very crunchy". Tam Dai Song appears to like and dislike Crunchtastics at the same time when he tries the elvin snack in Stellarlune.
They were given to Tam by Glimmer as they were waiting for Trix to appear in Book 9: Stellarlune.