To counteract the effects of sitting for long periods of time, I prefer doing some direct glute work. This helps with my posture and gets me back to center. One of my favorite exercises is the glute bridge. They can be done from anywhere and there are a ton of variations that you can try to keep them fun and interesting.
When I got uncomfortable from sitting for so long on a recent road trip, I would start flexing my glutes to the beat of the song as I was driving. Alternating from one glute to the other or both. It was actually a pretty good workout and gave me something to keep my mind off of how much longer I had to drive.
Below are some glute bridge variations that you may not have tried before.
Glute Bridge W/ Squeeze
Glute Bridge W/ Leg Cross
Glute Bridge W/March
Glute Bridge W/Alternating Overhead Reach