The best thing to do is get away from the hustle and bustle and enjoy some of the amazing nature.
Walk around Macritchie Reservoir which will take 2-3 hours depending on your pace. I would always get there at the crack of dawn before the hordes arrive and the creatures scurry away. At times during the walk you will be away from the water and feel like you are in a dense jungle.
A few miles off the coast of Singapore you will find St Johns Island and Kusu Island which are stunning beyond belief, barely nothing there apart from one food place on Kusu but amazing beaches and some nice walks. You can find the ferry schedule here:
https://islandcruise.com.sg/ferry-schedule/
Another place to take a ferry is Palau Ubin where you can take a cycling trail and maybe see the wild boars that roam free but be careful of your belongings.
Sungeu Buloh Wetland Reservoir is quite a nice walk and again if you get there at the crack of dawn you might encounter a saltwater crocodile!
For food I would highly recommend heading to Lau Pa Sat at night. From 7pm until midnight there are quite a few outdoor stalls preparing Satay on barbecues. It's an amazing experience and the food is incredible. I can almost smell the smoke as I type this!
Another great place to go for food and drinks (along with a spot of unusual shopping) is Golden Mile Complex which is essentially a huge Thai shopping place with bars and hawkers. Great food and good price drinks.
Also, don't be afraid to go to one of the housing blocks as most have a food court at ground level selling beers too at a very reasonable price. We used to frequently head to Block 468 on North Bridge Road which is a short walk over the river from Lavender MRT. Some great food to be had in there.
There are local football teams in Singapore too that generally play games at night. We adopted Albirex Niigata as our local team to support, the quality was pretty poor but was always a good night out when combined with a bite to eat and plenty of drinks.
If you're going to Little India then take a stroll down Dunlop Street where you will find some really quirky bars and restaurants. The bar which was a fave of mine when I lived there is called Olibier Rooftop Bar.