How to check woocommerce single product tag

To check if the product has the tag, you can use has_term() or is_object_in_term().

has_term( 'tag_slug_or_ID', 'product_tag' )

Or:

// checking if the product has any tag
is_object_in_term( $product_id, 'product_tag' )

// checking if the product has a given tag
is_object_in_term( $product_id, 'product_tag', 'tag_slug_or_ID' )