I'm here to assist you in categorizing rewards, jessica42.
The cashback reward isn't considered as your self-employment income. If you downloaded this transaction, you can tag them as personal income or personal.
You can record and account this transaction once file your taxes or when you transfer your data into TurboTax. Additionally, this is the link so you can see all the categories in QuickBooks Self-Employed.
Please post again if you need more help. Have a great day!