What's consuming the rest of your time? I bet you have an hour or so to spend at the gym before or after work if you really want to. Or could you do it during your lunch break? Also, you'll want to change what you eat--the Mountain Dew isn't going to help you. (Not bragging, but I'm a full-time graduate student with two part-time jobs and still manage to work out for about an hour a day--and I still have time to make my own dinner, which lots of people also insist they don't have time for. You might try that, too. In fact, I grow (most of) my own dinner in the summer, too. On the other hand, I don't have kids or anything that might require more time at home.)
If you still insist that you don't have time to work out, do it on the way to work: ride a bike instead of driving (or taking the bus/train/etc.). Maybe add in an extra ride over lunch. Lots of people, myself included, do this where I work. Even better, do it for all your errands and you'll save on gas, too.
You'll have to put in some effort, and the chances of you being able to do that at a sedentary job aren't that great. But it's worth it. You'll feel better in the long run.