title: Get WooCommerce product SKU in product pages meta box
body: <p>I have a custom meta box in the backend of WooCommerce. Currently I have it setup to display some data from the single product page.</p>
  
  <p>I've used <code>&lt;?php the_title(); ?&gt;</code> to display the title of the product and I've used <code>&lt;?php the_field('myfield'); ?&gt;</code> to display some content from an ACF field.</p>
  
  <p>I really want to be able to display the SKU in this meta box as well, but everything I've tried breaks the page.</p>
  
  <p>I tried adding <code>&lt;?php echo $product-&gt;get_sku(); ?&gt;</code> and it breaks the page. I've tried a bunch of other stuff to.</p>
  
  <p>I just need to pass the value of the sku on the inventory tab to a meta box on the same admin page.</p>
  
  <p>Can anyone else with this? Thanks.</p>