More than one million people have been affected by the disaster and President Anura Kumara Dissanayake has declared a state of emergency.
Sri Lanka's military has deployed helicopters for rescue operations, while humanitarian aid is flowing in from foreign governments and non-governmental organisations.
But it will be a long journey to recovery for Sri Lanka, which has seen its fair share of turmoil in recent years.
Mr Sahan also considers the kitchen as an "extension" of his volunteer work in 2016, when torrential rain and floods killed 250 people across the country.
Volunteers have compiled hundreds of requests for help, sent it to authorities, and organised the distribution of food to residents, Mr Sahan says.
"Whatever we asked for, we got more than enough in response from the community," he says.
A flurry of activity is also happening online, where social media users have created a public database to direct donations and volunteers.
Another volunteer-backed website helps donor find relief camps and what is most needed in those areas.
Private companies have organised donation drives, while local television channels have launched an effort to provide food and basic necessities like soap and toothbrushes.
Facing criticism over his handling of preparations for Cyclone Ditwah, President Dissanayake has urged Sri Lankans to "set aside all political differences" and "come together to rebuild the nation".
Opposition politicians have accused authorities of ignoring weather warnings, which they say exacerbated the disaster's impact.
On Monday, opposition lawmakers staged a walkout in parliament, claiming that the ruling party was trying to limit debate on the disaster.
On the ground, however, there remains a sense of unity as Sri Lankans pick up the pieces after the floods.
"In the end, the joy of helping someone else to save lives makes that tiredness fade," Mr Sahan wrote in a Facebook post on Monday, after putting in long hours at the community kitchen in Wijerama and other relief sites.
"Disasters are not new to us. But, the empathy and capacity of our hearts is greater than the destruction that occurs during a disaster."