Ways to earn money from gift cards

Hello everyone so I’m running this contest at work where if they sell a certain amount of a certain item they revive a $20 gift card and I do this 2 times a week and get fully reimbursed by my job. My question is what could I do to possibly make money off this like maybe buy from a certain store that gives cash back? I do have a card that gives me 1% cash back in all purchases so there’s that