Why I have a bad breath smell I brush my teeth every day one time but I eat chocolate everyday is this the cause or what?

No. There may be an underlying reason for your bad breath such as an abscess, an infection, localized food impaction due to gap (especially small gaps) between your teeth. The reasons may even related to your medical health. Brush once a day is good enough but you need to have a dentist exam for other reason. If the situation cannot be resolved, schedule an appointment with your medical doctor.
Mixture. The bad breath comes from a number of different bacteria in your mouth. Some produce sulfur still others create different smells, but finding a way to control their population is the best treatment. Brushing more often, brushing the far back reaches of your tongue, having your teeth cleaned professionally, and targeted mouth rinses can all benefit you. Chocolate should not be the issue.