Students have every right to spend the grant however they want on clothes, cars whatevers.
The grant is there to support a student in getting an education, not to fund their social life. Cars are a luxury and the grant should not be funding cars for students who are too bone lazy to walk to college or get the bus etc.
If a student is using their grant to buy a car, they don't need the grant. They are clearly able to afford rent, bills and other college expenses.