Here's a delightful free mockup piece: Coffee Cups Mockup. The PSD template is authentic and is a free resource to help you add your favorite brand and showcase it with style to impress your client in awe.

The design is aimed at making easy to add your branding. Just double click the smart object layer on the very top and add your design and save. More details of customization is in the help file contained in the download.

File Format: .PSD
Layers: Smart-Object
Dimensions: 5500x4000 Pixels
File Size: 133 MB