You may think that coffee and working out don't mix very well because caffeine can make you dehydrated. It's actually been proven that the caffeine in coffee only has mild diuretic effects and does not lead to dehydration. But caffeinated drinks can still make you jittery, sleepless, or anxious, which is why water is always your best bet for staying hydrated before and after a workout.
And in terms of after your sweat session, coffee might actually reduce muscle pain since it blocks the body's receptors for adenosine, a chemical released in response to inflammation. So if you want to work out, and have your coffee too — go for it! Just be sure you don't wreck your coffee with calorie-hefty add-ons like cream and sugar!