How do you record cash as a bank deposit with no relationship to an invoice?

I can show you how to add this cash transaction as a bank deposit, nbriteyes.

You can go to the Chart of accounts to add a transaction directly to the bank account as a deposit. 

Here's how: 

1. Hover to the Transactions menu and select Chart of accounts. 
2. Select the account where you want to add this deposit by clicking View register from the Actions column.
3. At the very top of the list, select the Add journal entry, Add check, or Add deposit dropdown menu below the Date and select Deposit.
4. Enter all the necessary information.
5. Click on Save once you're done. 

Refer to this article for more information about adding a transaction to the account register: Manually add transactions to account registers in QuickBooks Online. 

Meanwhile, here's how you can find, filter, sort, and edit transactions in an account register: Find, review, and edit transactions in account registers in QuickBooks Online. It also guides how to edit transactions and make quick edits from an account register. 

Let me know in the Reply section if you need more help adding this transaction to the bank account. I'm always here to answer them for you. Have a great rest of the day!