You may at times get someone walk in off the street to purchase a product or 2.
This is for the use case where they are not a current member in the system. You can either use the Store App to do this or the Control Panel. Both techniques you can charge cash or credit card.
Control Panel
Products -> Charge a Guest
Follow steps to enter customer information and payment method
Select product and then Charge Now to complete
Store App
In Coach Mode, add desired products to cart, hit the checkout button
Select 'or charge guest' on the Select Member screen
Follow the flow to complete purchase.