It's yeast and as long as you stay clean you won't get a rash or anything. It just builds up or grows in moist places. It's normal.
I occasionally have the same thing. I have larger breasts and it's usually under and inbetween them and especially if I sweat or like after I've been sleeping. It never happens after I shower but if I miss a shower or like I said I sweat or it's hot out or something when I come to bed at night and take off my bra I smell it a little bit. It doesn't smell bad, like you said it smells sweet. I'd like to know what it is as well.
I am not sure, I would get it checked by a doctor.