Move within your available work space as feasible: walk or jog in place and/or move your arms
Move creactively in the Corridors and inspire others.
If you are shy, start squats in the bathroom.
Go up and down staircases. If you must take the elevator, march while riding!
Break rooms, cafeteria, other available spaces.
If feasible, coordinate activity breaks with your office mates.
Move chairs and desks to have access to more space
Try a Paper dance competition: Use a newspaper to dance on.
Keep folding the newspaper and see who can dance on the smallest piece of paper!