I'm dealing with the same thing... Here are two things that have helped me....
Taking a nap in my car. I know it's a little cold out now (depending on where you're located), but you can put a blanket and a pillow in your backseat, and set your alarm for 30 mins... That cat-nap will really help you out.
Also, eat snacks all day long... Fruit, or pretzels, or anything that will keep your blood sugar level up, will help you not to crash.
If all else fails, you can have 2 caffeine drinks/day. I suggest tea with honey.