Can you cut back on the coffee a bit, and get an extra hour or two of sleep each night?
I used to get about 6 hours of sleep a night, start to nod off over my desk at about 3 pm, and my coffee intake would increase dramatically in the last couple hours of the work day as I tried to stay awake.
Now I get about 7.5 hours of sleep a night, and even with about half the coffee I used to drink, there is no nodding off over my desk in the afternoon. The extra 1.5 hours of sleep makes quite a difference for me.