A few ways, in no particular order:
1. You can get some minor NETS FlashPay (or EZ-Link) rebates for your MRT rides from
Travel Smart Rewards.
2. The
NETS Savers mobile app offers some minor benefits.
3. You can collect
CabRewards points when you pay for Comfort and CityCab taxi rides using a registered NETS FlashPay (or EZ-Link) card. (However, I might wait a few days, until 2017, to register your card since sometimes you can qualify for a registration promotion of 1,000 CabRewards points. I think the points expire every calendar year. Check the T&Cs.)
4. UOB is still (apparently) offering a $2 rebate if you top up your NETS FlashPay (or EZ-Link) card with a UOB MasterCard at a General Ticketing Machine. Expires December 31, 2016.
5. You can get a
free speaker if you auto top-up your NETS FlashPay card twice. Promotion expires March 9, 2017.
6. Some credit cards offer a rebate for auto top-ups of NETS FlashPay cards. One example is UOB's Delight credit card. The rebate is either 3% (if you have total merchant spending of at least $400 per month) or 0.3% for that particular card. OCBC's Frank credit card, with its integral NETS FlashPay function, is similar except the 3% rebate (if you qualify) is only applied to two auto top-ups per month. The Bank of China Family Card offers a 5% rebate on the first 4 auto top-ups per month, subject to minimum spending of $500/month.