Officers took action after noticing advertisements on social media, which said the recently-distributed spending vouchers could be converted into cash for a fee.
Pretending to be interested customers, officers arrested the trio in Mong Kok, Sham Shui Po and Tseung Kwan O on Friday.
The men, aged 33 to 45, claimed to be shop owners or salespersons.
The force said it will track down people who had converted their spending vouchers with the trio, and may make more arrests.
The payment platforms concerned will be contacted, and the shops may be blacklisted.
The police warned the public that they might commit conspiracy to defraud, if they conspire with shops to fabricate transaction records and cash out consumption vouchers.