Casual lunch between Atlanta and Augusta
I think I'm too late, but you've already discovered then that the space between Atlanta and Augusta is a no mans land of highway. Getting off around Lake Oconee is probably your best bet, but this stretch of highway truly is one to make sure you have lots of gas because of the lack of options.
If you could wait it out a bit, best option is probably to stop in Aiken, SC and explore downtown. My folks live there and I love all the little restaurants downtown. Just park and take a stroll, eating anywhere that suits.
Sorry that I missed this, but for the next time you're on this stretch of I-20 around lunchtime, try Crowe's BBQ in Madison (exit 114) or Holcomb's BBQ in Greensboro (exit 130). And keep our barbecue map bookmarked - it will be very helpful in the future!