Pros
Sonic is a great place for a person without much experience to get experience and people skills required for other jobs. The money really isn't to bad, and if you work hard you can make decent tips.
Cons
Unreliability of fellow coworkers - Several of my coworkers would not show up for their shifts, and when they did you didn't know if they were going to be in a great mood or not. Our cook would have moments where he would cry, and throw fits at least once a week and this would stop production and make work stressful. Management problems - My managers would always pick favorites in employees. If they were favorite they would not be expected to work as hard, and would receive free food. No down time on shift - Towards the end of my time working for Sonic I would work 8 or 9 hours with no break in the middle. While I can handle this, it was pretty exhausting. Promises of promotion - Again towards the end of my "career" at Sonic I was told I would be promoted to shift leader becuase of my hard work, and the area manager was working on getting me a small raise. Two months later there was no promotion, and I realized I had just been told this to keep me working for that store a bit longer.