Things got nice and sloshy in Pittsburgh Wednesday -- where Penguins players and fans teamed up to chug beers right on the street during the Stanley Cup victory parade!

Players like Trevor Daley and Ian Cole slammed brews on their pickup truck -- while Jake Guentzel made a beer-swiggin' deal with fans ... I'll sign your can, if you chug the brew.

Shocker, the fan agreed to the terms of the deal.