A list of 10 energy boosting foods:

1. Vegetables
2. Whole-grain Cereals
3. 100-percent fruit juice
4. Dried fruit
5. Fresh fruit
6. Nuts
7. Whole-grain pasta
8. Turkey or peanut butter on whole-grain bread
9. Water
10. Coffee


The whole article can be found here, discussing the benefits of these foods:
10 Energy Boosting foods

this is a great list to help you get through the work day. I think a mix of complex carbs and a little protein is the best thing to do so the energy lasts for a long time.