Looks like full-size drinks. Can't believe I've only just discovered this and it hadn't been posted! Yet another "ice cream van" style tour, loving these! If you click on the first link at top of the timeline you can find details, most of the locations have been and gone now including my local one yesterday (grrr!) but there's still:
London Canary Wharf - Saturday 21st
Birmingham Bullring Shopping Centre - Mon 23rd
Milton Keynes The Centre MK - Wed 25th
No details on timings but no voucher is needed, you just turn up.
Also you can book for free drinks to be sent to your house or workplace! Follow instructions on Facebook site.