add_filter( 'aioseop_title', 'aioseop_mod_wc_title', 10, 1 );
function aioseop_mod_wc_title( $original_title ){


$sku = '';
$title = '';

global $post;
if( 'product' !== $post->post_type || ! is_single() ){
return $original_title;
}
$title = $post->post_title;

$sku = get_post_meta($post->ID, '_sku', true);

$meta_title = "$title – $sku";

return $meta_title;
}