what can I do to make extra money?

I don't know the environment in your office. But in ours, there are no vending machines and the store is below the building. So people have to get in the elevator because we were in the 41st floor and buy something on the ground floor which was very expensive. I talked to my boss if it's ok if I put and sell some food and to my amazement, he approved. So I sell food from cookies to instant coffee then gradually increased my product by selling lunch by taking their orders before the day and put them on a styro. Then I searched about what to sell, I found an accessory shop so I sell accessories online through Facebook until now. There are a lot of ways to earn money as long as you're willing to put hard work and be serious in it.