Especially popular during the Showa Period (1926 – 1989), Dagashiya are retro candy shops that you can still find across the country (although numbers are sadly dwindling). You will find all kinds of ultra-cheap packaged eats from hard candies to mini jellies and even savory bites like soy sauce-based rice crackers. They all typically come bite-sized and individually wrapped so you can try a variety of treats.
Once you find your favorite, I recommend purchasing a few more to bring back as souvenirs!
Learn more about dagashiya: https://en.japantravel.com/guide/a-guide-to-dagashiya/68900