Yes, Spirit Airlines absolutely allows you to bring your own snacks on board for no additional charge. Since Spirit is an ultra-low-cost carrier that charges for all onboard food and beverages (and does not accept cash for them), bringing your own food is a highly recommended way to save money. You can pack solid food items like sandwiches, fruit, nuts, and chips in your "personal item" or carry-on bag. It's important to remember that any liquids or "spreadable" foods (like yogurt, peanut butter, or hummus) must comply with the TSA's 3-1-1 rule if you are bringing them through security. However, once you are past the security checkpoint, you can purchase any food or drinks in the terminal and carry them onto the plane. Just be mindful of fellow passengers and avoid bringing foods with extremely strong odors, as the recycled air in the cabin can make "fragrant" snacks quite overpowering for your neighbors.