That's a beer advertising truck, alright, with what appears to be a powerful sound system. Here's a larger image. Blatz resumed brewing beer in 1933, after the 21st Amendment was ratified. I wonder whether this truck was created in 1933, on a 1931 pickup chassis, to proclaim the event? Note the custom paint job (light fenders) and, despite the extreme customization, whitewall tires.
