Body odour is a cause of the bacteria in the body, splitting up the proteins into certain acids. Hygiene and genetics are also a factor that may contribute to sweat and body odour. Arm-pits are the common most areas with such odour.
Using an anti-bacterial soap daily could help reduce the bacteria count and hence reduce odour. Personal hygiene, like taking a bath daily and towel drying completely could reduce body odour. Clean clothing keeps the unpleasant smell away. Spraying a deodorant or anti-antiperspirant does not prevent the sweat but helps managing it better, masking a fragrance.