There may be cases when a store needs to sell items that are not part of the WooCommerce inventory. Below are two options for selling 'miscellaneous products' in WooCommerce POS.
POS Only Miscellaneous Product (recommended)
Using the POS Only feature, you can create a 'miscellaneous product' for use in the POS. The title, sale price, regular price, tax rate and meta information can all be changed on-the-fly during checkout.
Fee line item
Using a Fee line item is similar to creating a POS Only Miscellaneous Product. Cashiers can quickly update the title, price and tax rate of Fee. The main drawback is that Fee's may appear separate to products in your reporting.