How to load product by SKU in magento 2

The correct way, according to Magento 2 service contracts, is using repositories:

$product = $this->productRepositoryInterface->get($sku);

Use Magento\Catalog\Api\ProductRepositoryInterface to get it in your constructor.

Full example:

...
private $productRepository; 
...
public function __construct(
    ...
    \Magento\Catalog\Api\ProductRepositoryInterface $productRepository
    ...
) {
    ...
    $this->productRepository = $productRepository;
    ...
}

public function loadMyProduct($sku)
{
    return $this->productRepository->get($sku);
}
...

Note:

If the product does not exists, this method triggers a NoSuchEntityException error as it would be in the best Magento2 practice.

So, if you need to handle somehow, wrap it in a try/catch block.

Instead of using the object manager directly, inject the ProductFactory:

public function __construct(\Magento\Catalog\Model\ProductFactory $productFactory)
{
    $this->productFactory = $productFactory;
}

Then use it like this:

$product = $this->productFactory->create();
$product->loadByAttribute('sku', $sku);

or to do a full load (the above loads it using a collection):

$product = $this->productFactory->create();
$product->load($product->getIdBySku($sku));

I like @phoenix128-riccardot 's answer, but would add an exception, just in case the product does not exist:

try {
    $product = $this->productRepositoryInterface->get($sku);
} catch (\Magento\Framework\Exception\NoSuchEntityException $e){
    // insert your error handling here
}

I was not able to add it as a comment (too low reputation), sorry.