If I'm at home, udon noodle soup: just vegetable stock cube in a pot of water, boil it, chuck the noodles in, chuck in whatever you want to put in the soup (I just chop up tofu and one vegetable of my choice), boil for a few mins, and it's done. Put Laoganma on to serve. Obviously use whatever other noodles you prefer if you have a preference other than udon. Takes like 15 mins total and it's so simple for something that's an actual full meal. I don't take it with me when I'm on the go though, as it's hard to carry a bowl of noodle soup with you.

For something you can take with you on the go, I've been making this vegan smoked tofu carbonara recipe lately. You'll still need a microwave to heat it up once it's lunchtime, unless you want to eat cold spaghetti for lunch, but it's really tasty, especially the tofu.