i work in a downtown environment with dozens of easy to walk to restaurants for lunch, so i almost always eat out for lunch because i can't be bothered to plan meals ahead of time and then bike to work with them. typically lunch is a salad with meat and/or eggs, or a sandwich with meat or eggs, or chili in the colder part of the year. and i always make sure to have plenty of snacks around the office like fresh fruit and hard-boiled eggs.

basically it's all about meat/eggs (protein, protein, protein) and fruits/veggies (vitamins, vitamins, vitamins).