Not always. You can download the Sonic app on mobile or access it through the web so you can order and pay for your food online. You can use the app to find nearby restaurants, as well as coupons and offers.
You can also create a My Sonic Profile that establishes you as a loyal member of their brand. You can get special offers, redeem coupons, and get free treats on special dates such as your birthday! Aside from that, you can also buy a My Sonic Card, which gives you discounts and other opportunities for all Sonic chains.