Buy X Get Y Free With auto add the same product in the cart

Question

How to implement the custom functionality without extension i.e Buy X Get Y free. If customer buy the 2(X) quantity then the third (Y) will free and the third product will automatically add in the cart with the amount zero(Free product)

If the free extension are available for this( Buy X Get Y free) please share the link.

Am using magento 2.2.2

Answer 1

If you Add Free Product in Cart When Add Perticular Product In cart. So You Can Use Event Observer For Add Free Product in cart.

events.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
    <event name="checkout_cart_product_add_after">
        <observer name="add_free_product_to_cart" instance="Vendor\Checkout\Observer\AddFreeProductToCart" />
    </event>
</config>

Observer: AddFreeProductToCart.php

<?php
namespace Vendor\Checkout\Observer;

use Magento\Framework\Event\Observer;
use Magento\Framework\Event\ObserverInterface;
use Magento\Catalog\Api\ProductRepositoryInterface;
use Magento\Checkout\Model\Session as CheckoutSession;

class AddFreeProductToCart implements ObserverInterface
{
    protected $productRepository;
    protected $checkoutSession;

    public function __construct(
        ProductRepositoryInterface $productRepository,
        CheckoutSession $checkoutSession
    ) {
        $this->productRepository = $productRepository;
        $this->checkoutSession = $checkoutSession;
    }

    public function execute(Observer $observer)
    {
        $item = $observer->getEvent()->getData('quote_item');
        $product = $item->getProduct();
       
        if ($product->getSku() == '306081-0142') {

            // Add the desired product (SKU '620001-01') to the cart
            $productIdToAdd = '620001-01';

            $productToAdd = $this->productRepository->get($productIdToAdd, false, null, true);

            if ($productToAdd && $productToAdd->getId()) {

                $quote = $this->checkoutSession->getQuote();
                $productToAdd->setPrice(0);
                $quote->addProduct($productToAdd);
                $quote->collectTotals();
                $quote->save();
            }
        }
    }
}

When You Use This Event-Observer Then Solve Your Problem For Buy X Get Y Free Product..