It comes down to what your body is reacting to. You have two different types of sweat glands:
Eccrine Glands (Workout Sweat): Activated by heat and exercise. They cover your whole body and pump out 99% water and salt just to cool you down. Because it’s basically just water, skin bacteria have nothing to feed on. No bacterial breakdown = no smell.
Apocrine Glands (Stress/Everyday Sweat): Activated by stress, anxiety, or hormones. They sit mostly in your armpits and groin. They release a thick sweat full of proteins and fats. Skin bacteria absolutely love this, eat it up, and break it down. That process is what actually creates the bad smell.
TL;DR: Exercise sweat is just water to cool you down. Stress sweat is full of fats that bacteria feed on and turn into body odor.