funny money
noun /ˌfʌni ˈmʌni/
  /ˌfʌni ˈmʌni/
[uncountable] (informal, disapproving)- a currency (= the money used in one country) that is not worth much and whose value can change quickly- They are just pumping billions of funny money into the economy.
 
- money that has been illegally printed, stolen or has come from illegal activities; money that is not real because it has been created for a game- Police seized more than 5 million dollars' worth of funny money.
- playing poker with funny money