On Malaysia Airlines - a full meal service is provided since not everyone in the country is Muslim. There is no change to their inflight meal services with a choice of 3 main courses in Economy - pretty unique for ANY carrier - and alcohol continues to be served - pretty unique for an Islamic carrier!
During Ramadan, having just travelled with them, they seem to try and accommodate any Muslim passengers who may be fasting by starting their meal service a little later than usual (if it is almost time to break fast) but if this is not possible, continue with their routine service. Passengers may choose to skip the meal service which would not be unusual for any airline - and I guess - unfortunately the meal is wasted.
When it was time to break fast (at sunset), it was great as the crew came through the aircraft with an extra 'snack' service according to flight timings and this was available to all passengers regardless if you had stuffed you face already.
On the domestic run KL-Kota Kinabalu, just before landing, the crew announced that it was time to break fast and handed out cake (package in neat parcel-boxes) and drinks - as we prepared to land that evening.