If you want to create a one-time item that isn't currently on your menu, you can create a custom item.
1) To make a custom item, you need to click on the custom icon on the home screen.
2) You can add the custom name and custom price here.
3) Type in the desired item and cost. Click on the "Add to Cart" Button.
4) You can see the custom item added to the order. Note that the item will not be stored in the menu. You can only use it once.