Milkshaking - Wikipedia

Philosopher Benjamin Franks suggested that the use of particular foodstuffs in political protest had historically been a practical matter, noting that whilst "nowadays, carrying raw eggs to a nationalist meeting would require some backstory to justify it if challenged by the police", until recently carrying a milkshake would not have aroused the same suspicion. He also argued that milkshaking "is clearly effective in making the victim feel uncomfortable and look ridiculous".

See also: French Revolution

How does one do this without getting a beat down?

Asking as an American where our trigger happy cops will wrestle you to the ground, and then scream self defense as they punch you repeatedly in the back of the head.