I dont have a "scientific" answer for that but I'm pretty sure is it normal :).
Maybe everything in that frappucino such as the milk, cream, flavoring just makes it smell bad.
"Eat a certain food, get a certain smell" !
1.could be guilt
2. they are not social
3. shy
Well what is your side of it first
Typically between the ages of 9 and 12 or what many consider late prepubest and early puberty