I used to find that I always had a hard time refocusing after lunch.
Now I play Root Beer Tapper. If you grew up in my generation and spent as much time with video games as I did, you'll probably remember it. If you didn't, you're probably better off.
Anyway, every day after lunch I play four games and then get back to work.
My high score is around 48,000. See if you can beat it.