In the late aughts, Fruccola was one of the pioneers of fast casual dining in Budapest with a special focus on healthy foods and salads. They have since become a recognized brand and a mini chain with three locations across the city. Besides salads, smoothies, and fresh fruit and vegetable juices, Fruccola also makes excellent breakfast omelets, both with salmon and spinach & goat cheese (€5). On weekdays, they serve a seasonal, two-course lunch prix fixe (€6) that's heavy on vegetables, but not strictly vegetarian.
Note that this location isn't open on weekends, unlike the one on Kristóf tér, which is only a 10-minute walk from here.