A Muslim customer was left "vomiting for days" after claiming his Burger King double cheeseburger was "loaded" with bacon.
Gundogdu Yuzudik, 22, claims he had repeatedly asked for staff to not include bacon in his meal.
He says he was unable to eat for days after the apparent mix-up on January 11.
He said after taking one bite into his double cheeseburger he found it was stuffed with bacon.
The fast-food fan shared his ordeal on TikTok and says he has avoided bacon his entire life for "religious reasons".
However, other social media users have claimed that Burger King's cheeseburgers are not halal anyway.
In a video, which has been viewed more than 64,000 times, Gundogdu told the burger chain to "sort their staff out" as he felt that his "simple" instructions were not followed.
Gundogdu also reveals that he was left "vomiting" and suffering headaches and claims it has impacted his mental and physical health.
The Stansted airport employee said he was shocked he was offered "two free Whopper meals" as an apology, after vowing to never return to Burger King again.
Burger King has since apologised for the error and said they are retraining their team to 'minimise' mistakes like this.
Gundogdu, from Enfield, Greater London, said: "I was on my lunch break and I headed to Burger King to get a double cheeseburger.
"I specifically say with all my meals 'no bacon', and it's always been correct. I told this to the till lady a couple of times, and when I got my food, I didn't expect otherwise.
"It was a simple instruction. It's a mistake and we're all human, but it wasn't busy so they weren't working under pressure so there wasn't a reason for them to have made a mistake.
"It's just down to basic instructions. We're all human, we all make mistakes, I appreciate that.
"When I went to eat my burger, I took a bite and it didn't taste right. I opened the bun and it was loaded with bacon.
"Even the smallest bite made me feel mentally and physically sick. For three days after, I wasn't eating properly.
"I was physically hungry but I couldn't eat without vomiting. I was feeling sick.
"The thought of the bacon made me feel sick. Even when I'd be chewing anything, I was automatically thinking it was bacon.
"The first day, I didn't eat. By the third day, I was slowly getting back to eating. I was starving, but I physically and mentally couldn't eat anything.
"It'd been my plan that I was never going to eat it in my life. I didn't know whether I was going to have an allergic reaction. That's how important it was to me.
"I went back to the Burger King and complained, but they weren't very helpful. They just apologised and that was it. Nothing else, which really shocked me."
Gundogdu decided that further action was required, and shared his experience on Twitter and TikTok.
Gundogdu said: "I took it to Twitter and posted pictures on there until Burger King got back to me. They apologised and gave me a link to email them.
"It took days for them to get back to my email complaint, and all they did was apologise and offer me two free Whopper meals. I thought they were taking the p*ss.
"Burger King's response really shocked me, that it was just an apology. I told them about my mental health and how I didn't eat for three days.
"I emailed back saying 'you've not taken my mental health or religion into consideration'. Nobody's done anything regarding the situation.
"This has 100% put me off going back. I'll never go back to Burger King again."
At the time of his visit, Gundogdu admits he didn't realise that Burger King didn't serve halal meat - meaning the meat is not considered "permissible" under Islamic law - but says he is not a strict Muslim.
Gundogdu said: "A lot of people on my TikTok were telling me that Burger King isn't really halal, which I didn't really know about.
"I thought any meat that wasn't pork was halal. I'm Muslim but I'm not really religious. I don't pray, so I don't really know a lot about it.
"My biggest shock came from how much bacon was on there. Even my friends were shocked.
"All of my friends sympathised and 80% of my TikTok comments were sympathetic, which surprised me. It's sad because it feels like nobody is taking this seriously."
Several TikTok users empathised with Gundogdu's predicament.
One wrote: "Even if the burger isn't halal it's the principle."
Another commented: "Eating bacon is so traumatising. You're not overreacting, I suffered too. It's just unbearable, and the disbelief too."
Other commenters weren't as sympathetic and chastised Gundogdu for eating at Burger King in the first place.
In his video, which has been viewed over 64,000 times, Gundogdu says: "I was on my break, so I went to Burger King Airside to get a burger meal.
"So I ordered a double cheeseburger meal and I specifically said 'No bacon' twice to the cashier.
"Got my meal and went back to my crew-room to eat it on my break. So I bit my burger, first bite. I'm chewing it, but I'm thinking 'This does not taste right at all'.
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"Open the bun and find it's loaded with, full of bacon, yeah. And I'm 22 years old. I've never ever ever eaten bacon in my entire life, and I'm never planning on eating bacon.
"It's just for like religious reasons, it's just not in my thing and I've never eaten it and never will, so that needs to be appreciated and respected, I believe, in my f**king way. So here are the pictures now.
"So first, I want to show you this, on the wrapper of the burger, they've specifically crossed this out, so no bacon.
"That's my first proof and that's the first mistake that they've done. Anyway...I've obviously finished my chips, this is the burger that I've obviously had first bite of it.
"And then until I realise, I find this on my burger. How? How? Can someone like explain this to me? It just doesn't make sense. I just do not understand.
"But I do want to say that I've not been eating anything for the past three days.
"I've been physically sick, I've been vomiting, I've been having headaches. Because I've never ever eaten it in my entire life, and I was never planning on eating it.
"This is absolutely ridiculous. So I do want to give a big shout-out to Burger King, if you're going to watch this, because you will be tagged in this.
"You need your staff out, you need to let them know that they need to listen to simple instructions that they have been given by customers really."
A spokesperson for SSP, who operate Burger King's Stansted airport branch, said: "We're committed to providing passengers with a great experience at our restaurants, and we’re sorry to have fallen short on this occasion.
"In light of this incident, we will be retraining our team and making sure all customised orders are double checked before they are served to help ensure it doesn’t happen again. We have been in contact with the customer to apologise directly."
A spokesperson for Burger King said: "Burger King UK understands the impact and upset this incident has caused Gundogdu Yuzudik and sincerely apologises for this unfortunate human error.
"Staff are trained to follow customer specifications to ensure they can have their meal their way and we will be reinforcing our training at all restaurants, to guarantee mistakes like this are minimised. Burger King UK strives to deliver the best customer experience and highest-quality meals possible at all times."
