Leftovers from dinner. (Have microwave at work)
Fruit
Nuts/trail mix that I mix
Water

If no leftovers, I might make a sandwich but for dinners, I usually double recipes so there are leftovers for lunches.

Leftovers

Cheese, crackers, and an apple

Tin of sardines, nuts, apple, and maybe some kind of roasted veggie.

Simple. Cook extra for dinner and pack it for lunch.

Honestly I just bring leftovers which most of the time need to be heated. Sorry.

But I would definitely look into bento box lunch ideas, on pinterest, tiktok, etc. A lot of those can be eaten cold, I feel like it's always a sandwich, veggies and dip, crackers and cheese/deli meat, etc.

And look up recipes for things you can meal prep and just eat cold. Couscous and noodle salads come to mind.

I hate dealing with Tupperware etc at work so just a sandwich, a piece of fruit, and chips/ crackers.

Today was a pretzel roll with good wuality maple ham cold-cuts (i put it together.) Under 400 cal and delicious.

Leftovers if have them and it's something that can be reheated in the microwave.

Sometimes a can of soup.

I try to keep a few frozen meals from Trader Joe's around to bring if I don't have leftovers. Usually the Indian ones. I like almost all of them, but the eggplant and chickpea ones don't come with rice so I have to remember to pack some naan with those.

Does it have to be hot?

One thing I like which reheats really well is to make a big pot of farro or barley with better than bullion vegetable flavor. Then I just mix in tons of roasted vegetables. If I have time I roast them myself but if not Costco sells big bags of roasted vegetables that are great. You can also mix greens into this.

I can stand meat reheated in microwave so this works well for me.

About once a week I just take an Icelandic yogurt with a cup of berries and some granola. Another day I might do an apple, an Rx bar, and maybe another piece of fruit or cheese stick. Or those humus with pretzel chips packs plus an apple.

Take some cans of soup from Progresso.

I either make sandwiches: butter, cheese, or salami or more often pack yesterday’s dinner leftovers. I usually cook with the intent that there will be leftovers and we use them as next day lunch or dinner.

Today was a tuna sandwich, peanuts, and a few prunes.

If hot it's leftovers.

If not hot (more often) it's a bagged salad with some added protein (either shredded rotisserie chicken, or maybe some dumplings if it's the Asian-inspired salad kit)

Mostly leftovers, so today, sloppy Joe's made with ground turkey + broccoli

Always accompanied by fresh fruits and veggies as a side, or, if I'm hungry a mid-morning or mid-afternoon snack, some combination of baby carrots, celery sticks, snap peas, sliced peppers, etc., and an apple, peach, plum, nectarine, sliced strawberries, blueberries, grapes, etc.

In summer, mostly green salads with leftover protein from dinner the night before

Winter, I tend to make big pots of things, put them into single serving containers and throw them in the freezer. In my rotation, which I make double-batches of every time:
Ham and Bean soup
Vegetable soup
Stew made with butternut squash, chicken peas, lentils, diced tomato and cumin. You could leave out the tomatoes
NYT chicken and artichoke stew (so good and so easy)