In the late aughts, Fruccola was one of the first restaurants to pioneer fast casual dining in Budapest, especially within the healthy segment that specializes in salads and fruit juices. Fruccola has since become a recognized brand and a mini-chain with three locations across the city. Besides salads, smoothies, fresh fruit and vegetable juices, Fruccola also serves excellent breakfast omelettes, both with salmon and spinach & goat cheese (€6). On weekdays, they offer a seasonal, two-course lunch prix fixe (€7) that's heavy on vegetables, though not strictly vegetarian.
Note that this location, in Arany János Street, is closed on weekends, but there's another one on Kristóf tér, a 10-minute walk from here.