Documentation: https://developers.trustpilot.com/invitation-api#create-invitation(s)
API for Invitations: Walkthrough

Service + Product Example:

{
  "referenceNumber": "test123",
  "consumerName": "Test Customer",
  "consumerEmail": "tester@test.com",
  "serviceReviewInvitation": {
    "preferredSendTime": "2013-09-07T13:37:00"
  },
  "productReviewInvitation": {
    "products": [
      {
        "sku": "SKU-FOR-SHOE",
        "name": "Red Shoe",
        "brand": "The Big Shoe Store",
        "imageUrl": "https://i.ibb.co/jk8BSQ7/big-red-shoe.png",
        "productUrl": "https://www.bigshoestore.com/big-red-shoe"
      }
    ]
  }
}

Just Service Review:

{
  "referenceNumber": "test123",
  "consumerName": "Test Customer",
  "consumerEmail": "tester@test.com",
  "serviceReviewInvitation": {
    "preferredSendTime": "2013-09-07T13:37:00"
  }
}

Just Product Review:

{
  "referenceNumber": "test123",
  "consumerName": "Test Customer",
  "consumerEmail": "tester@test.com",
  "productReviewInvitation": {
    "products": [
      {
        "sku": "SKU-FOR-SHOE",
        "name": "Red Shoe",
        "brand": "The Big Shoe Store",
        "imageUrl": "https://i.ibb.co/jk8BSQ7/big-red-shoe.png",
        "productUrl": "https://www.bigshoestore.com/big-red-shoe"
      }
    ]
  }
}