"One of these bonuses..."

Not me, but a friend of mine (among others I'd assume) managed to get an entire sales campaign cancelled that a bank in my country did.

IIRC the bank tried to promote one of their debit cards (which are basically prepaid credit cards) via some bonuses and gifts you'd get as a customer, e.g. one of 20 products you can choose for free if you start using it etc.

One of these bonuses they offered was a small payback, you'd get after each purchase. What they did was basically round up the amount you paid (to full Euros) and give you the difference.

So if you bought something for 27.63€ you'd get 37 cents gifted from this bank.

What he then did was only possible because we were university students back then, had very flexible work time and some of our friends were temping in supermarkets... he went to the supermarket our friends worked at times when basically no one else was there and purchased hundreds of single potatoes. Each one = one purchase with the card. Depending on their weight each of these potatoes was like 2ct or 3ct, so for each purchase he got 98ct or 97ct gifted from the bank, making him profit about 94-96ct for each potato.

He got about 250€ (plus an unreasonable amount of free potatoes) in 2 days with this until the bank called him like "uh... could you like maybe stop that...?" and he just shamelessly responded "why?" to which the bank person on the phone had no good answer. So then he just went on and made some more money until the whole incentive thing got completely canceled a few days later.

Fun times.

L_Flavour

"There were several vending machines..."

There were several vending machines at my school and around town that had an exploitable design flaw. You could take two bills and scotch-tape them into one long bill, one face up and one face down. When you put the bill in the machine, it would read the first bill correctly and the credit would show up on the machine, then it would try to read the second, but since it was upside down, it would then spit both bills back out, and I could buy what I wanted with the credit it read from the first bill.

LowCalPal

"If you take the survey..."

If you take the survey on the back of the Popeye's receipt, you get a free two-piece and biscuit with the purchase of a drink. And you can take the survey on the back of that receipt to get a free two-piece and biscuit with the purchase of a drink. And you can take the survey on the back of that receipt to get a free two-piece and biscuit with the purchase of a drink. And you can take the survey on the back of that receipt to get a free two-piece and biscuit with the purchase of a drink. And you can take the survey on the back of that receipt...

boygriv

"One day..."

I don't know if this counts as a loophole but when I was in high school my buddy worked at Subway. This was when they had the rewards card that you filled out with stamps and after eight subs you got a free one. I guess the employees were supposed to trash them when they were redeemed but he just put them all in a box. One day he gave me a box full of them and I ate free subs until they discontinued the rewards card years later.

05110909

"Went home..."

A supermarket in my town has a little bar inside of it that's run by the supermarket (they use the same payment system). The supermarket was running a coupon that took $3 off of every purchase, no matter how much money you spent. They were also having a sale at the bar where pints of locally-brewed stout were $1 (typically they'd be about $6). My friend and I bought three pints, total price was $3.21 (tax). Subtract three dollars with the coupon... 7 cent pints of really good beer.

Went home, came back with a bucket. Bought three at a time. Spent just over $2 for 30 pints of beer. Had a great night. Tried to go back the next day but they'd caught on and gotten rid of the coupon.

camocardigan

"This indicated whether or not..."

When my brothers and I were 6-10 years old we found a crane candy game where you were "guaranteed to win" something. We found a laser sensor in the area where you pick up your prize. This indicated whether or not something had dropped. So, by holding the flap door open at the bottom the sensor was never triggered so for 25 cents we nearly emptied the machine. Thanks Red Robin!

sparke16

"Since the products were open..."

When I worked at Target, I'd buy 2-3 games at a time. Some of them I'd play for a few hours before deciding I didn't really care for it. Since the products were open, I couldn't return them to Target. I learned that Walmart would exchange the game for you, no questions asked without taking the wrapping off the new game. So I'd take my opened games to Walmart, exchange them for unopened games, then take the unopened game back to Target and return it for the full price.

bangersnmash13

"Basically..."

Last year my local burger chain had a promotion for one week where you could get a free order of fries, no strings attached. You went to the online store and there was a "Free Fries" item that you could add to the cart. Being a web developer, I took note of the exact network request made when you clicked "Add to cart".

Basically, the request looked like "POST /cart { itemId: 672 }" where itemId 672 corresponds to the free fries item.

Well, after a week, they took the free fries off the menu. But, I still had the web request saved, and to my amazement, calling the request directly with the correct itemId still added the free fries to the cart!

Now, a year later, I've claimed 30+ orders of free fries, over $100 of value. Every time I go to order from the store I cross my fingers praying it's not been fixed yet, but at this point, I'm not sure they ever will address this.

CharminUltraStrongTM

"Had no student debt..."

Right out of college I worked a job that had a 100% match to any retirement contributions. I was young, lived rent-free with my parents, Had no student debt, and could grab OT nearly every week. After some budgeting, I figured I could throw 80% of my paycheck into retirement. I did so for 9 months until my supervisor called me into the office to sign a policy change that limited retirement contributions to 50%. I'd stashed away nearly $35,000 on about a ~$32,000 annual pay. I had no life for about a year, but damn if it didn't jump-start my retirement.

gorgonheap