Born and raised here, my go-to cheap weekend list that's actually good, not just "go park" filler: 1) The green corridors and connectors, the Rail Corridor end to end, or cycling the park connector network (PCN) from say East Coast all the way round, rent bikes cheap or use your own, it's a proper half-day out for free. 2) Southern Ridges walk (Henderson Waves etc), gorgeous and free. 3) The free museums, many national museums have free entry for citizens/PRs, great for a hot afternoon. 4) Pulau Ubin day trip, cheap bumboat over, rent a bike, feels like old Singapore, brings you back. 5) Hawker centre food adventures, pick a famous hawker centre you've never been to and just eat your way through, a whole experience for under $15. 6) Library programmes, the public libraries run free talks, kids activities, and it's aircon and free. 7) Sungei Buloh or the reservoirs for nature. 8) Free community events, check your CC (community centre) and the arts calendar, there are constant free performances and festivals. The trick is Singapore has TONS of free stuff, you just have to look past the malls. Nature + hawker food + free museums fills every weekend cheaply.