How to update multiple invoices array.

Solution

We can use the foreach to update the multiple invoices array.

On the constructor use the function

public function __construct(
    \Magento\Sales\Api\InvoiceRepositoryInterface $invoiceRepository
){
        $this->invoiceRepository = $invoiceRepository;
    }

On the execute function foreach each invoice and set the value.

 foreach($invoices as $invoice) {
     $invoiceData2 = $this->invoiceRepository->get($invoice);
     $invoiceData2->setData('variable', 'value');
     $invoiceData2->save();
 }

So through this, we can update multiple invoices.

Thank you.