How to use sprintf() instead of concatenate

Before:

$variables['users'][] = 
$user->field_first_name->value . " "  . 
$user->field_last_name->value . ", " . 
$user->field_user_designations->value . ", " . 
$user->field_user_specialty_designation->value;
            
  
After:

$variables['users'][] = sprintf("%s %s, %s, %s", 
$user->field_first_name->value,
$user->field_last_name->value,
$user->field_user_designations->value,
$user->field_user_specialty_designation->value
);