Silk is a brand of soy milk. There are also a number of specialty flavors including a coffee flavor (called soylatte).

Silk give the following information on caffeine content:
There are 55 mg of caffeine in one 8 oz. serving of Silk Coffee, 75 mg of caffeine in one 11 oz. serving of Silk Coffee, 3.6 mg of caffeine in one 8 oz. serving of Silk Chocolate Soymilk, 45 mg of caffeine in one 8 oz. serving of Silk Mocha and 0.3 mg in Silk Chai Soymilk.