I make up dry mixes for muffins, gallettes, bread etc in jars - then it's just a question of dumping the appropriate number of tablespoons into a bowl with egg/fromage frais etc and 2 minutes in the microwave.
As to the rest - it becomes second nature after a while. I've got used to cooking at the weekend and freezing half of everything I cook.
Supermarkets provide tuna, prawns, yogurt, tomatoes, celery, carrots, lemons, cottage cheese etc on those days when I forget to take lunch - if you have a microwave at work prawns, spring onions, coriander and lemon juice are transformed in to Thai style soup in minutes.
I also carry emergency supplies in a packet of my handbag - a pack of biltong, a small tin of tuna with a ring pull, a sachet of mustard, some packets of splenda, a napkin and a plastic spork.