The drama, based on the novel Before I Die by Jenny Downham, sees Fanning play Tessa Scott, a Brighton girl who is diagnosed with terminal leukaemia. She compiles a list of things she wants to do before she dies, with losing her virginity at the top of the list.
In the one-minute video above, Fanning and Skins star Kaya Scodelario, who plays Tessa's best friend Zoey, are seen swiping a credit card from a businessman at a cash point.
Jeremy Irvine, Olivia Williams and Paddy Considine are among the supporting cast for Now Is Good.
The movie will open in UK cinemas on September 19.