Food prices soared.

Prices for necessities such as rice, sugar, and salt were controlled by the Japanese Military Administration Department (M.A.D). They set the maximum prices for these goods and announced them in the newspapers and in notices around town.  (explaination)

When the Japanese occupied Singapore in 1942, they introduced the military yen. The new currency was commonly referred to as “banana money” because the $10 note featured a banana plant. The prewar British currency was still legal tender but was quickly replaced by the new Japanese currency in the open market.22 The initial issue of “banana money” was serially numbered with control letters and safety features such as a watermark and security thread.23 Subsequently, large quantities of the currency were issued without security features and the serial numbers disappeared from the notes. The military notes were intended for circulation on par with the Straits and Malayan dollar notes, but their value decreased dramatically over time. By 12 August 1945, the exchange rate had dropped to 950 Japanese military dollars for 1 Straits dollar.24 The Japanese currency was rendered worthless when it was demonetised by the British after they regained control of Malaya in September 1945.25 ]
I can infer that British changed the Japanese currency so called “ banana note”  (  p )
This can be seen in the source that “By 12 August 1945, the exchange rate had dropped to 950 Japanese military dollars for 1 Straits dollar.24 The Japanese currency was rendered worthless when it was demonetised by the British after they regained control of Malaya in September 1945” ( Ev )
The british did not use the japanese currency after japanese surrender ( E )

During the war, the Japanese turned all the Worlds into gambling farms, encouraging Chinese businessmen, such as the Shaw Brothers, to operate gambling dens at the amusement parks. As these dens were precluded from raids, the bright lights at the Worlds continued to attract many gamblers and the dens were often crowded. The popularity of the gambling dens helped the Japanese profit substantially from the revenue collected from tax and licence fees of the gambling dens. The Japanese were not allowed in the gambling dens, but they could patronise the cabarets and nightclubs. When rumours about the Japanese surrender were rife in August 1945, the gambling stalls in all the Worlds closed down.