Add Amazon product with variations

Question

I am trying to upload amazon product with variations, but is it even possible in same feed to upload product with variations, or I need every variation to add as a product and then make relationship with some product, but that would take too much time if I have so many variants. If I try like this it says that this child doesn't have SKU, but in which moment I need to add SKU for variation.

  $fileContent = '<?xml version="1.0" encoding="utf-8" ?>
        <AmazonEnvelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                  xsi:noNamespaceSchemaLocation="amzn-envelope.xsd">
                <Header>
                  <DocumentVersion>1.01</DocumentVersion>
                  <MerchantIdentifier>' . $merchantIdentifier . '</MerchantIdentifier>
                </Header>
                <MessageType>Product</MessageType>
                <PurgeAndReplace>false</PurgeAndReplace>
                <Message>
                  <MessageID>1</MessageID>
                  <OperationType>Update</OperationType>
                  <Product>
                    <SKU>'.$amazonProduct->master_sku.'</SKU>
                    <ProductTaxCode>A_GEN_NOTAX</ProductTaxCode>
                    <DescriptionData>
                      <Title>'.$amazonProduct->title.'</Title>
                      <Brand>'.$amazonProduct->distributionChannelTeam->brand->name.'</Brand>
                      <Description>'.preg_replace('/[^a-zA-Z0-9]/', ' ', $amazonProduct->description).'</Description>
                      <MSRP currency="EUR">25.19</MSRP>
                      <Manufacturer>Example Product Manufacturer</Manufacturer>
                      <ItemType>'.preg_replace('/[^a-zA-Z0-9]/', ' ', $amazonProduct->product->baseProduct->category->name).'</ItemType>
                      <CountryOfOrigin>DE</CountryOfOrigin>
                      <UnitCount>1</UnitCount>
                      <PPUCountType>stück</PPUCountType>
                      <IsExpirationDatedProduct>false</IsExpirationDatedProduct>
                    </DescriptionData>
                    <ProductData>
                        <Home>
                            <Parentage>child</Parentage>
                            <VariationData>
                                <VariationTheme>Size-Color</VariationTheme>
                                <Size>XS</Size>
                                <Color>Dark Grey Melange</Color>
                            </VariationData>
                        </Home>
                    </ProductData>
                    <IsHeatSensitive>false</IsHeatSensitive>
                  </Product>
                </Message>
              </AmazonEnvelope>';