For flexibility, there are a lot of stretches that are easy to do discreetly at the office.
A great one to try is a multi-tasker!
Sit facing forward, then turn your head to the left and your torso to the right, and hold a few seconds.
Repeat this process 15 times, alternating sides, and feel your tension melt away as you stretch out your back, shoulders and nearly every muscle from neck to hip.