Some product prices were reduced to nothing on Thursday evening in a suspected glitch.
Items such as pasta sauce, coffee and cookies were listed for free in a pricing error on the app.
Some customers were able to access the supermarket's wares for free for as long as "a few hours".
Products listed at no cost included Loyd Grossman pasta sauce, Costa ground coffee and Fox's biscuits, while other items were reduced, such as Robinsons squash falling from £1.50 to 15p per bottle.
Other discounted items included Air Wick reed diffusers, which were being sold for just 55p instead of £6, and Nature Valley cereal bars, which were on sale for 75p, down from £1.90.
Peter from Lancashire told he was able to buy over £80 worth of goods for the cut price of £3.29, which included delivery fees.
He said: "I was surprised the Co-op and Deliveroo honoured and delivered the mispriced items."
Instead of keeping the products for himself, Peter said he would donate most of them to his local foodbank.
Another user said: "Got myself a lot of cheap bits from the co op. 15p Robinsons squash will do well with the heatwave.
A Co-op spokesperson told BBC News: "A small number of prices were showing incorrectly on our Deliveroo shop for a few hours last night. This was quickly resolved, and we apologise for any inconvenience caused."
It was recently revealed that the Co-op was affected by a cyber attack, one of many retailers including Marks and Spencer and Harrods to be hit by such attacks.
Co-op staff were told to keep their cameras on during remote meetings and verify all attendees, while being warned no recordings or transcriptions should be taken.
However, it is not thought the cyber attack and Thursday night's price changes are linked.
Retailers are not always bound to honour purchases of products advertising lower prices in error, though this depends on their terms and conditions.
Many do uphold pricing errors for products, though, such as in 2022 when some copies of Fifa 23 Ultimate Edition were available for purchase at just 4.80 rupees, or 5p.
Publisher Electronic Arts (EA) said it would honour the huge price reduction.
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