According to a report at Vocativ by Inna Lazareva and Noam Binshtok, some Atheists are even fasting during Ramadan just so no one will catch on.
Back in the mid-1990s, I arrived in Kuwait on the first day of Ramadan. I was there on a 6-month contract to install a Novell network. I didn't even know what Ramadan was. The airport was packed with Kuwaitis leaving the country to avoid Ramadan (as I later found out). So it seems that many Muslims, like many Christians, aren't really very religious.
Anyway, I was warned against eating or drinking -- or even chewing gum -- in public until Ramadan was over. Even though, in that area of the KOC (Kuwait Oil Company) compound, we were all non-Muslim foreigners, we still had to hide to eat lunch.
The Quran says that there should be no coercion in religion but the rules of Ramadan apply to non-Muslims too -- even in a foreigner compound. It sure seemed like coercion to me.
I imagine that plenty of real Muslims fake fast, too. It seems like the sort of thing that the Muslim equivalent of a fuzzy, cafeteria Christian would do.
Considering the risks to life and liberty for athesists in muslim countries, I woudn't be surprised if people fake fast, fake pray, and fake everything else.
Not that people in christian countries would fake their religious observances.