These champions of green practices buy takeaway meals in reusable containers, use reusable menstrual products and choose to eat less meat.
Their eco-friendly habits have attracted snide remarks such as "it's a hipster trend", "it's a cult" and "it's something only rich people do".
But Ms Maria Tan, Ms Chuang Xue Ying and Ms Goh Yu Xuan - all 24 - are not fazed. And they want to encourage others to do the same.
The trio, who met in school and through mutual friends, chronicle their sustainable lifestyle on their shared Instagram account, Back to Ground Zero, which they started at the end of 2017.
Ground Zero, they say, refers to their grandparents' kampung days, when life was simpler and more community-based.
Tips for an eco-friendly lifestyle at home and at work
1 Keep it streamlined
Keep reusables such as containers, utensils and water bottles in a tote bag, so you can just grab the bag when heading out to buy food.
2 Plan your grocery shopping
Take along a reusable bag so you can refuse single-use plastic bags at the supermarket. If you shop at the wet market, take along reusable produce bags and containers to hold vegetables, seafood and meat.
3 Watch the trash
Separate your trash into reusables, recyclables and disposables. It allows you to see which area you need to work on the most. To further reduce food waste, set up a compost bin or find a community composting bin in your neighbourhood to dispose of your vegetable scraps.
4 Think before you buy
Before you buy a new or replacement item, think about whether the existing one can be repaired or mended. Buying second-hand items from thrift stores or online reselling platforms such as Carousell may also help you save money.
In those days, for instance, meals were packed and shared in metal tingkats, or food containers, instead of today's styrofoam and plastic boxes.
Ms Tan is pursuing her master's in business analytics at Imperial College Business School in London, while Ms Chuang and Ms Goh recently graduated from National University of Singapore and Singapore University of Social Sciences respectively.
Ms Goh says: "The louder we are with the eco-movement, the louder people who are against it will be.
"But we don't have to hard-sell this way of life. We just keep practising it and people will get curious. That's when we can start conversations."
On their Instagram account, they share tips on reducing waste, suggest eco-friendly alternatives to common plastic items and highlight like-minded green companies and activities.
But they also share their struggles and failures on the platform.
"It's important to highlight these too because you don't have to be perfect - no one is. Sometimes, you slip up and use a disposable item, but you don't have to be too hard on yourself," says Ms Tan.
One of their biggest struggles is making an impact at home, where they live with their parents and their influence is not as strong.
But that does not stop them from trying.
Ms Chuang, who adopted a vegan diet two years ago, says her parents initially did not understand what veganism - abstinence from using animal products - was or why she was doing it. But they have grown to accept it.
"My parents' generation is all about convenience. Because people were busy, plastic disposables became an essential part of their lives. They know it's bad for the environment, but they do it out of habit, so you have to remind them," she says.
It was slightly less challenging for her two friends, whose family members jumped on board early on.
Ms Tan's family has a compost bin - where food scraps are broken down by worms into nutrient-rich organic fertiliser - to reduce their food waste, while Ms Goh and her three sisters have experimented with vegetarian diets.
Although she prefers not to put a label on it, Ms Goh describes her diet as "climatarian", which is choosing to eat based on what is least harmful to the environment.
On Sept 7, the trio will be holding their first eco kampung-style festival at Ground Up Initiative, a non-profit organisation in Yishun.
The Ground Zero Festival will feature live music and workshops that teach participants, among other things, how to make their own shoes and eco-friendly slime.
There will also be a marketplace with local brands such as zero-waste grocery store Unpackt and vegetarian restaurant Well Dressed Salad Bar, and an exhibition area.
Last September, they held a smaller and more marketplace-focused event called Ground Zero Market in the same location. They opted for a more experience-based festival this time.
"While it's good to have stalls selling eco-friendly items, we don't want to encourage overconsumption of these products. It's better to have people come together to share knowledge and learn things," says Ms Chuang.
The festival, which is funded by the National Youth Council's Young ChangeMakers grant, will be wholly run by volunteers.
The goal is to inculcate a sense of eco-friendly living in visitors, whom they hope will be from all age groups and backgrounds.
Ms Tan says: "Living sustainably is not just about saving the planet. This lifestyle can also be enjoyable - people can live with a lot less and much simpler than they think."