Drink black coffee. Not too much, not too little. Don't put milk in it. Just drink it black.
Cold water. Drink something like one cup every hour. Maybe even more.
Eat filling and satisfying food. Grain products, rice (rice cakes work too), potatoes, salads, foods rich in protein and fat.
Have a proper posture when sitting. Use a stool or something with no back support if you can.
Greetings from a fellow office worker. Accounting for lyfe, of course.