Rowdy Riot is a energy-drink that was sold in Greg's school's lunch room.
Rowdy Riot is explained by Greg Heffley to have been sold at the lunch room for a long time. However, when the school began a campaign to switch the junk food with healthier food, Rowdy Riot was banned. The kids who drank this energy drink became dazed and confused. Some even had to visit the school nurse due to getting the shakes. The kids protested, but the teachers would not relent.
Later on, a kid named Leon Goodson purchased a large quantity of Rowdy Riot drinks and began to sell them drug-dealer style, three bucks a pop. Many of the Rowdy Riot addicts were willing to pay, and they take their Rowdy Riots to recess. There, they secretly drank them behind a wall.
However, a supervisor named Mrs. Lahey discovered them and forced them to stop drinking and pour the Rowdy Riot out. As soon as she was gone, though, the desperate addicts used their socks to mop up what of the energy drink that they can and squeezed it into their mouths.
Rowdy Riot is contained in a tall can that bears its name in the middle of a large starburst. It appears to have no other features, although some sort of nutrition facts label may be present on its unseen back side.
Due to a quote from the book that claimed that "the red dye makes the kids hyperactive", it is presumed that Rowdy Riot is dyed red in color.