Friska told FEMAIL it had been trying to contact the customer to apologise.
Reddit user M1BG shared a snap of the egg on toast they'd ordered from Friska, which comprised of undercooked toast and eggs strewn across a cardboard takeaway box.
M1BG said he was "hoping for a little more effort" in his breakfast after he forked out for a hearty portion of eggs on toast.
He posted: "Tbh I was hoping a little more effort would have gone into my £5.70 eggs on toast breakfast from Friska at Luton Airport [sic]."
Bristol-based company Friska's slogan is "feel good food", and they have ten other locations across the country.
The Reddit user's photo has received hundreds of comments from people mocking his food.
One posted: "That is proper sad to look at. Look at the state of the toast! For £5.70 I hope they hand fed you!
"Seriously that is appalling and i hope you complained," another commented.
A third wrote: "My local butty shop does a full english for the same price. This made me want to cry."
"That is bloody awful. That's what you get for trying to leave this country!" another joked.
However, others said the holidaymaker was expecting too much from overpriced airport food.
One commented: "I know it seems that airports are generally ripping people off, this is to some degree true but one has to keep in mind that there are fees that come with trying to open a business at the airport that are extremely high - airports charge businesses an arm and a leg so they need to have very high prices to actually make a profit."
"That's £5.70 in airport money. On the street, it's about 35p. And honestly, what do you expect for 35p?" another said.
A third wrote: "The only thing you should buy at an airport is bottled water everything else is a rip-off. Actually makes my blood boil when whoever i'm with wants an organic salad for £9.40."
A spokesperson for Friska said: "We've seen the thread and this is far below our usual standards at Friska. We're trying to get in touch with the customer to apologise directly for this and also with the franchise team who run our Luton airport store."