There are multitudes of candy bar brands all over the world, and several sub-types of candy bar within each brand. The additional details section includes a list from A to Z chosen randomly from multiple countries. No candy bar starting with a Q or an X was found.
Almond Joy, Butterfinger, Charleston Chew, Dove Bar, Eat-More, Fry's Turkish Delight, Green and Blacks Hazelnut and Current, Haviland Thin Mints, Idaho Spud, Junior Caramels, Kit Kat Milk Chocolate, Lindt Lindor Extra Dark Chocolate, Milky Way Simply Caramel. Nestlie Yorkie Raisin and Biscuit, Oh Henry!, Payday, (No candy bar starting with a Q found), Reese's Peanut Butter Cups, Snicker's Peanut Butter Squared, Twix Milk Chocolate Cookie Bars, U-NO Bar, Violet Crumble, Whittaker's 5 Roll Fairtrade Creamy Milk, (No candy bar starting with an X found), York Peppermint Patty Drops, ZERO bar.
Choosing one type for each letter is not a comprehensive or totally representative list. The list could be narrowed according to country, type (milk chocolate versus white chocolate, for example), or popularity. Distinctions could also be made to separate between the general brand name and individual product names. Given the broad parameters of the question, the selection demonstrated above is extremely random.