I did it this way:
// Initial weight
$weight = 2;
// Student's book entity
$student_book_entity = $node->field_student_book[LANGUAGE_NONE][0]['entity'];
// Get Student's book ISBN and alter some attributes
$student_isbn_field = array_merge(field_view_field('commerce_product', $student_book_entity, 'field_book_isbn'), array(
'#field_name' => 'field_students_book_isbn',
'#title' => t('Student\'s Book ISBN'),
'#weight' => $weight++,
)
);
$node->content['field_students_book_isbn'] = $student_isbn_field;
// Teacher's book entity
$teachers_book_entity = $node->field_teacher_book[LANGUAGE_NONE][0]['entity'];
// Get Teacher's book ISBN and alter some attributes
$teacher_isbn_field = array_merge(field_view_field('commerce_product', $teachers_book_entity, 'field_book_isbn'), array(
'#field_name' => 'field_teachers_book_isbn',
'#title' => t('Teacher\'s Book ISBN'),
'#weight' => $weight++,
)
);
$node->content['field_teachers_book_isbn'] = $teacher_isbn_field;