The versatility of lemons makes them useful even when you're not at home. The Kitchn has a list of reasons why you should consider taking a lemon with you with your lunch bag, from flavouring water to dressing a salad.
Flavouring water is probably our favourite use, since you can slice the lemon when you need it, wrap it or put it in a plastic bag, and then use it again later. The post also suggests using your office lemon in tea, to brighten up leftovers or dress a salad for lunch, or even as the primary ingredient in that lunch (they mention an avocado sandwich that sounds pretty good).
The drink suggestions are enough to make designating an office lemon worthwhile though -- if you don't care for the flavour of water, adding a little lemon can make all the difference. Hit the link below for more ideas.
Eating at the Office: Pack a Lemon in Your Lunch Bag [The Kitchn]