it can be due to what they are eating(your diet),
alcohol
Cruciferous veggies
red meat
spicy foods
asparagus
these foods can make you smelly by going out of your pores
also Body odor is actually the fault of the bacteria that live in sweaty areas of your body. Bacteria thrive in moist environments, like your armpits. When you sweat, the bacteria break down certain proteins in the sweat into acids. So, it's not the bacteria that stink.