Islamic authorities announced the start of the fasting month with the sighting of the crescent moon in countries such as Indonesia and Saudi Arabia.
Marking the divine revelation received by Prophet Mohammed, the month sees Muslim faithful abstain from eating, drinking, smoking and having sex from dawn to dusk.
They break the fast with a meal known as iftar and before dawn have a second opportunity to eat and drink during suhur. The month is followed by the Eid al-Fitr festival.
In Madaya, where some 40,000 people have been living under government siege for months, resident Mumina, 32, and her husband planned to break the fast using UN food handouts.
Also Read
The package contain pulses and tuna cans but "there's no pasta, no meat, no dairy. We tried to plant some vegetables but the land isn't good for planting now," she said.
"There's barely any food in the markets and whatever we find is so expensive that we can't buy it," she said, planning a simple meal of beans for Monday night.
"We definitely have a lot of choices," he said trying to put a brave face on things.
"There's parsley, radishes, coriander, arugula, spinach, and sometimes we can find zucchini," he said. "But there are other people who don't even have these options."
An estimated 8,000 people live in Daraya which received on June 1 its first aid delivery since a regime siege began in 2012, but British charity Save the Children said it excluded desperately needed food.
In the Iraqi city of Fallujah, father-of-six Abu Mohammed al-Dulaimi also worried about how to provide food for his family during Ramadan.
An estimated 50,000 people are believed trapped inside, some being used as human shields by IS, and the families left behind are often those who could not afford to leave.