Which food item must be discarded after a customer has used it, according to health regulations?

A bowl of cocktail sauce is the correct answer because it is classified as a potentially hazardous food item when served in a communal setting. Once a customer uses the sauce, there is a risk of cross-contamination. Bacteria from the customer's utensils or hands can be transferred into the sauce, making it unsafe for subsequent customers. Health regulations prioritize food safety by ensuring that items that can be contaminated and shared among multiple customers are properly discarded after their initial use.

In contrast, items like a plate, salt and pepper packets, and a glass of water do not typically pose the same immediate health risks upon use. Plates can be sanitized and reused, salt and pepper packets are single-serve and can be safely reused, and water can be refilled if served in a clean manner. Thus, the requirement to discard a bowl of cocktail sauce specifically reinforces the importance of preventing the spread of pathogens in food service environments.