The bad smell in a dishwasher is usually caused by a few common issues:

• Food debris buildup and a clogged dishwasher filter, which trap food particles and cause odors.
• Grease buildup in the filter, drain, or interior parts.
• Drainage problems causing standing water, which leads to a sewage-like smell.
• Mold or mildew growth, especially around the door gasket due to moisture.
• Leftover food or dirty dishes inside the dishwasher.

Solutions include cleaning or replacing the dishwasher filter regularly, running dishwasher cleaner or vinegar rinse cycles, checking and fixing drain hose problems, removing leftover food, and keeping the dishwasher door slightly open to air out moisture after use. These steps help eliminate odor and maintain dishwasher freshness.