Deduct the rent expense on line 20a, Schedule C (Form 1040), line 20a Rent or lease: Vehicles, machinery, equipment.
In the TurboTax EasyStep interview, under Business Income & Expenses, scroll down to Business Expenses and select Other Common Business Expenses. Do not select Business Vehicle Expense for your rented car expenses. Scroll down to Rental Expenses and click the Start button. Select Equipment Rental, enter a description, such as "Rental car - 2018 Bentley" and the related expense.