On the go snacks?

Hand-held fruits like apples, bananas, and oranges work. Those branded cereal bars are easy to just grab and take one with you. Yogurts are pretty good for you and come in enough flavours to not get bored.

Or if you're willing to do weekly prep sessions, you can portion out things into baggies/containers to grab, like grapes, nuts that you like, or crackers & portioned out cheese.

If you're willing to do even more weekly prep, you can portion out salads, and keep the dressing in containers (I have some tiny ones that are perfect for it, and close right into the bigger salad container). Then they're ready in containers every morning.

If you have a microwave at work there's even more possibility! Tupperware containers make it so easy to bring leftovers, or cooked rice, veggies and meat to warm up with your fav sauce. Then you only have to worry about cooking supper (and it takes the same amount of time to cook 1 portion as 2!)

I am on the road quite a bit for my job. I have to plan ahead to stay within calories. My faves are:
String Cheese
Nuts (I keep a bag of natural Almonds in the car and can easlily count out 1/2 ounce, 13)
Small snack bags of carrots are in the produce department at the grocery store
Protein/snack bars, read labels some are pretty calorie dense
Once a week I make up 8 veggie trays with whatever I find at the farm market. Glad makes containers that have a small cup that fits in the lid. Low cal dressing for the dip and I have veggies and dip for about 100 calories

KIND bars

As others have said, careful with energy/protein/granola bars. Many are very calorie dense (e.g. a Clif bar is about 250 cals, with ~20g of sugar!)

I keep the following in my desk:
Almonds (Blue Diamond Salted Caramel or Toasted Coconut are AMAZING)
Jerky (I like Simply Snackin’ dried meat. Beef or Chicken with fruits added. They’re great and only 60 cal!)
Dry roasted edamame (Seapoint Farms brand)
Dry roasted chickpeas (The Good Bean is a good brand, but they're also not that difficult to make on your own ahead of time and season with whatever you like)

I keep these items in the fridge at work, and usually pair them with a piece of fruit (apple, orange, banana, pear, grapes):
Baby carrots
Cottage cheese
Nonfat Greek yogurt
String cheese
Turkey lunchmeat (reduced sodium)

Hard Boiled Egg! The best way to satisfy your hunger. It’s packed with protein and antioxidants… a perfect grab and go snack. This is what I usually take when I travel… with a pinch of salt and I’m one happy guy.