The amiibo cards can be found throughout the game or also can be purchased from particular shops. (nintendofuse.com)
They can only be used to buy things at particular shops. (young-money.org.uk)
When discovered the vodka was taken back and the shop keeper given a strong talking to by the parent but it seems that this particular shop us well known for happily selling alcohol to underage kids. (emmaand3.com)