How do I add a deduction for meals, that may not be used every pay period?

Thank you for connecting with the QuickBooks Community, Towerpizza. It will be my pleasure to guide you into adding a deduction for a meal. Here's how for Quickbooks Online Payroll:

1. Go to the Workers or Payroll tab, then click employees.
2. Choose the employee's name.
3. Select Edit, next to Pay.
4. In the deduction section, click Add a new deduction or + Add deductions.
5. Use the Deductions/contributions and choose New deduction/contribution. 
6. Choose a Deduction type and Type from the small arrow ▼ icon.
7. Enter the Provider name that appears on the paycheck.
8. From the Amount per pay period icon, choose $ amount or % of gross pay, and enter the $ amount or percentage. If necessary, do the same for the Company-paid contribution. 
9. Select Done, once finished.

If you are using Intuit Online Full Service Payroll, this article includes the steps to do so and explain how to select taxable or pretax deductions.

This way it will be added to the employee's profile, which makes it easier for you when doing your payroll. Please let me know if you have any questions or concerns. The Community and I are willing to assist you at all times. Take care.