Magento2 Refresh Cache for Single Product

You can use this code to refresh the cache for single product

$objectManager =   \Magento\Framework\App\ObjectManager::getInstance();
$productR =      $objectManager ->create('\Magento\Catalog\Api\ProductRepositoryInterface');
$product = $productR->get('product_sku');
$product->cleanCache();
$this->_eventManager->dispatch('clean_cache_by_tags', ['object' => $product]);

Please initialize the objectManager and ProductRepository in your constructor