Do I need a logo on the 20 unit challenge product?

You won't need a logo because there is usually an MOQ (Minimum Order Quantity) to do this

For the 20 unit challenge, you do not need to worry about having a logo on your product.

The main goal of this challenge is to learn the process of selling on Amazon, not necessarily to create a fully branded product. So, you can skip the extra expense and stress of creating and applying a logo for this challenge.

However, when you move forward with your main products, having a professionally designed logo can help set your products apart from competitors and build your brand identity.