How to get a product variant by SKU and get parent product details as well?
Untested, but something like this should work:

{% set products = craft.commerce.products({
  hasVariant: {sku: 'my-sku-number'}
}).first() %}


See: https://craftcommerce.com/docs/craft-commerce-products#hasvariant

If you only want to search the default variant of the product:

{% set products = craft.commerce.products({defaultSku : 'my-sku-number'}).first() %}


See: https://craftcommerce.com/docs/craft-commerce-products#defaultsku