This is a matter of culture, not just religion, so different countries will handle it differently.
I can tell you how it works in two countries:
In Egypt, which tends to have a late-night culture anyway, places of business (food and otherwise) shift their hours later. Restaurants that cater only to Moslems serve a lot of customers at iftar (sunset fast breaking), particularly because it is a big party time and most employers sponsor a big iftar get-together every year.
Restaurants open just before fast-breaking time, (so everyone can be seated and ready to gobble) and the food is put out. When it’s time to eat, people tend to wolf their food down immediately.
The meal eaten just before sunrise is called suhur, and it is also a big draw, though less so than iftar. Restaurants ofter special meals and promotions for suhur as well.
Egyptians love food and have many holiday traditions related to food. There are all kinds of delicious special dishes, especially sweets, eaten during Ramadan. People’s weight, and the money spent on food, both go up during this month. I wouldn’t be surprised to learn that a lot of restaurants make their largest revenue during Ramadan.
Things are somewhat more restrained in Indonesia. It is only a theory, but I have always thought that one reason why you don’t see the same kind of ravenous food attacks at sunset is because most of Indonesia is on the equator, so Ramadan fasting hours don’t change much over the years: it’s always about 12 hours, so the whole culture adjusts to the unvarying predictability of fasting hours. (Egyptians have to contend with long, hot, dry August days - when Ramadan hits during August, that’s considered the worst, because of the thirst as well as the long fasting period. But fasting month is a lot easier in February, when the days are cool and short.)
In Indonesia, at least in big cities, a lot of restaurants stay open during normal hours during fasting month in Ramadan. After all, there are a LOT of people who still need to eat - non-Moslems, women having their periods, anyone who is too ill or fragile to fast, pregnant or nursing women, non-observant Moslems, and people who are just plain cheating. Some restaurants put up curtains to make the eating going on inside a bit more discrete. I’ve asked several people what purpose these curtains serve: are they out of consideration for people fasting, so that they don’t have to be tempted by the sight of people eating, or are they to protect the people inside, who don’t have to advertise the fact that they are cheating/on the rag/ etc? Invariably the answer I get is: “both!”