Get all metafields for products

Retired Boards Appdev Metafields
26

But Shopify doesn’t allow to store SKU

Sure it does. You store things like SKU code on the variant.

So when creating a product:

POST /admin/products.json
{
  "product": {
    "title": "Burton Custom Freestyle 151",
    "body_html": "<strong>Good snowboard!<\/strong>",
    "vendor": "Burton",
    "product_type": "Snowboard",
    "variants": [
      {
        "option1": "First",
        "price": "10.00",
        "sku": "123"
      },
      {
        "option1": "Second",
        "price": "20.00",
        "sku": "123"
      }
    ]
  }
}