Could be two issues here - one is secreting an odour through the sweat glands, usually caused by eating something with a strng odour like garlic.
The other is incorrect washing or infrequent washing of clothing, which will allow bacteria to build. As looby says, sweat does not smell, but the bacteria that breed is stale sweat do.
Have a discreet word about washing freqeuncies, temperatures, and so on, and the effects that wrong temperatures or gaps in washing can have on clothing.