When a little imagination is used, old coffee grinds can be reused in various ways, as is exemplified by the Virus 'Stay Warm' Line.
The Virus 'Stay Warm' Line is a collection of athletic gear made from coffee beans. To be more exact, the Californian company uses what they call Coffee Char or Coffee Charcoal. All the grinds are processed into a natural fiber that allows clothes to be made with ease.
So what are the benefits? The use of Coffee Char will actually trap heat close to the skin by providing a base layer fabric. It actually increases surface temperature by 10 degrees, so it's fairly well insulated. The material also has UV-shielding and anti-odor features. This is a really interesting concept that re-imagines coffee into something completely different.