In 2010, Christina A. Roberto, a medical professor at the University of Pennsylvania, authored a study that found that small children are more likely to enjoy a food product that has a popular cartoon character on the packaging, particularly for "energy-dense, nutrient-poor foods." 

"These findings suggest that the use of licensed characters to advertise junk food to children should be restricted," she concluded. 

Five-and-a-half years later, Roberto is floating a similar policy proposal aimed at parents. Putting warning labels on soft drink packaging could significantly reduce the amount of soda American parents buy for their kids, she writes in a new report released in Pediatrics, the official journal of the American Academy of Pediatricians.