I would opt for a short nap of 10 to 15 Mins would be refreshing. I do that atleast on weekends. On weekdays I dont have the liberty as I would be in office.
Food habits: I would suggest go for less starch content food, Any food that contains lots of starch induces sleep. Take lots of leafy veggies that the food that contains fat. This keeps you smart. Food rich in proteins also keeps you smart. Have food that fills only half of your stomach. Then during late afternoon when you may feel hungry take some fruits. Also remember having lunch on time (and regularise your lunch break timings) reduces your fatigue and keeps you smart.
Don't exercise after a meal: Atleast for two hours from the time you had a lunch, do not exercise or go for a walk its really harmful to your health.
Let you hobbies empower you: This is the wonderful time to hone your skills by doing something which you have a flare towards. Do things which you would enjoy doing. In my previous work place we used to have a huge shopping mall besides my office. I used to do all my purchase by sparing some 10 Mins in the afternoon. Now in my preent office, I used to go to the library and read a few magazines and books.
These are few things which I usually do to win over a short nap on week days.