Hummus, my guy. There are also some shelf-stable bean dips.

Banana. Banana is good for you.

When I was in college, my go-to packed snack was home made Ritz PB sandwiches.

Just grab a sleeve of Ritz, take two, smear peanut butter between them, smash and repeat. Can churn out a dozen or so per minute, and eat them twice as fast.

Last I checked, Ritz crackers are vegan, so no modifications necessary.

These are pretty calorie and protein dense so they will do in a pinch but friendly reminder that balanced diets are important.

If you have a fridge at work, there's about a billion ways you can riff on a wrap that are quick to make, good chilled, and quick to eat

Finally there's plenty of ways to do the hiking classics of trail mix / granola that fits your bill. Bonus shoutout to granola because you can toss it on some yogurt to get something a little more rounded.

Peanut butter sandwiches will keep.

Also, don't sleep on fruit!

quick calories: sweet fruits, dried fruits

slower calories: pretzels and crackers

better calories: a fresh fruit and a whole grain sandwich with some spread, some condiments, some leaves.

classic low effort: the mix of nuts and dried fruits (like raisins)

Nuts and seeds alone are obvious, but they also have a lot of calories and may not provide calories that fast, so you can end up overeating. That's why I go for more starchy snacks from cereals, if any. Try to eat dense calories with more fiber, especially fat.

It also helps to have a bigger breakfast. Speaking of a nice porridge, there are all sorts of portable "oat bars" and similar things. Those can pack a lot of calories too, often too much. (You can make them at home, it's not that difficult.) If you can't find those, try looking for "work-out bars" that are plant-based.

And watch your weight. The need for snacks can be a sign that your breakfast was too small.

i personally keep a bag of soylent and a shaker cup for a quick nutritous meal. it comes out to like $2 per meal