In the US they're automated, I assume with some kind of laser/light sensor. If you pick up the drink/snack to look at it and put it back you get charged for it. (Picture)

 

Debbie Wasserman-Schultz Can’t Answer Why Voters Compare Unpolular Dems to ‘Slugs’ and Slow, Passive Sloths-Devolves into TDS Session Instead (Video)

BREAKING: Video of Physical Fight Between Female Secret Service Agents Outside Obama’s DC Residence Released… “I Whoop This Girl’s Ass!”