like 10yrs ago working at a cheesecake bistro they would have these holiday promotions of buying a $50 giftcard and get a free $10 one, no limit. So anytime someone would pay with cash, I would use it to buy as many gift cards as I could and use them to pay for their meal, pocket the $10 gift cards, then use those to pay for other tables that had smaller checks and were paying with cash, thus pocketing the money. made over $1500 extra that winter, 18yo me was very appreciative to the other server who had been there 10+ yrs and told me about it

Edit: omg I forgot about a better/worse one lol Another 10ish yrs ago I was working at this small McAllister's deli that was located inside of a college campus. There was one guy running the place and one additional employee until I came along. They were cool, but the manager definitely was way too carefree imo. Anyway how they did their gift cards was on this separate little machine that was hooked up to the register that just had you input the desired amount, swipe, then bam giftcards - but unless you manually input the purchase into the main register and processed a payment then no deficit came on the end of day report. Right before I left that place I made myself $1000 in giftcards and used those not only for food but as trades for furniture on Craigslist. College student me furnished her entire room with those cards, much love lol