"The girl drinks orange juice."
Translation:La ragazza beve succo d'arancia.
"Di" means it's made of, "a" means it's flavored with, and "con" that it also contains; in the case of juices they're made of fruit (hopefully!), while an ice cream would be flavored. In practice you can sometimes find "panino al prosciutto" and "panino con prosciutto"; "panino di prosciutto" would be wrong but that doesn't mean it's not used somewhere as well.