If it’s just two days, it’s really not even much of a roadtrip. Take yourself and a cell phone. Maybe some snacks, might want to have a good music selection or group of podcasts.
As for stops, Petersburg Battlefield could kill some time if you’re into Civil War History. The rest of your first day is pretty blah though. Your second day though is full of lots and lots and lots of awesome sights. The Georgia coast is amazing and you could spend a week in Savannah. It has art, food, history, beaches, just a gorgeous place. One of my favorite towns in the US. St. Simon’s Island is worth a stop. Pretty beach town, early settlement if you like history, normal beach stuff if you don’t. It has a Methodist retreat as well with a museum if you’re religious. Cumberland Island is a pretty place, but a little bit more involved of a trip.
If you’re just looking for a quick get up and move around stop, maybe try Hofwyl-Broadfield plantation north of Brunswick. It’s right off of 95 and doesn’t take too long. It’s not a gorgeous plantation house like you see around Charleston or New Orleans, but it will kill some time, get you moving and the mossy oaks are pretty and you can always tell people that you toured a plantation on the way down which is about as touristy southern as you can get.
Jacksonville itself is a hole, so you can skip through there. The only thing I can think of worth anything is Fort Caroline which is cool if you’re into early settlements, but if you are, then the next place is where you want to stop - St. Augustine. St. Augustine is a couple of things. First, it’s a tourist trap with Ripley’s and the Pirate Museum and plenty of beachy kitsch and you have to know that, but once you’re past that, it’s actually an awesome place to visit. Most of the town is built with Spanish Mission architecture which is beautiful. Lots of reds and whites popping out at you. The Cathedral is just amazing architecturally. Flagler College is an old Hotel that needs to be seen. There’s also tons of history. Castillo de San Marcos is a must see stop. The Shrine of Our Lady is worth a few moments. It’s a great town and deserving of a couple of days. The only other thing that I think is really worthy on that route is Kennedy Space Center.
Anyway, hope this gives you some ideas.
As an aside, when I do roughly that route, I usually just blow past the first day and get as many miles under my belt as I can so there is more time on the southern half of it.