What is the ONLY acceptable substance to clean the grills?

Hot water is the only acceptable substance for cleaning the grills at Five Guys because it effectively removes grease and food residue without introducing any harsh chemicals that could contaminate the food. Using hot water helps to maintain a sanitary cooking environment while ensuring that the grill's surfaces are properly cleaned. This method aligns with food safety regulations and best practices in the restaurant industry, making it the most appropriate choice for maintaining equipment cleanliness.

Other options, such as cold water, soap and water, and vinegar and water, may be effective cleaning agents in other contexts, but they either do not provide the necessary heat for thorough cleaning or introduce substances that are not suitable for surfaces that come into direct contact with food. Therefore, hot water is the clear and correct choice for grill cleaning in this scenario.