It is best to take your vitamins with a glass of water rather than a cup of coffee.
The issue with coffee is that it works as a stimulant and helps speed the passage of materials through your digestive tract. This means you won’t necessarily absorb all of the nutrients in your vitamins as you would if they moved more slowly through your system.
Coffee can also cause excessive urination, speeding the removal of water-soluble vitamins from your system. Try to finish your coffee at least 15-20 minutes before taking your vitamins; otherwise it is best to take your vitamins a few hours after finishing your coffee.