Hard to believe this was actually a question on Christianity Today. Thank God for the voices of reason, especially Doug Wilson.
"It is not appropriate to fast alongside Muslims. I wouldn't make a point, if I were in a heavily Muslim state where everybody is fasting during the day, of fixing a hot dog and walking outside and eating it … but to observe Ramadan along with your Muslim neighbors and friends, letting them know that you're observing Ramadan as an act of some sort of religious or spiritual solidarity, is simply a fundamental compromise. They're observing Ramadan in the service of a false God and a false gospel, and we shouldn't be trying to express our solidarity with that."
Douglas Wilson, senior pastor, Christ Church, Moscow, Idaho, and senior fellow of theology, New St. Andrews College