A sip of a beverage taken by someone while passing the beverage to it's rightful owner. The sip is taken as a "payment" by the person passing the drink. This action is most prevalent when one buys a beer from an aisle vendor while sitting deep in a row at a sporting event. Resulting "toll sips" are taken by your annoying buddies after the vendor hands it to them to pass to you.
"Hey Frankie! Pass me a beer, and no toll sips this time!"