Quite simply, Saijo is famous for its water. The city is said to have the tastiest water in all of Japan. Having not personally sampled water from throughout the country, I cannot attest to the validity of this statement.
Though, my first gulp of Saijo water, from a plastic bottle conveniently filled at one of the city's many public watering holes, was certainly a pleasant one. The water was crisp, cool, and refreshing. But honestly, in near 90 degree weather with insane humidity, even dirty pond water would have been pleasing.
Due to its first-rate water, Saijo is home to many sake breweries, as well as the Shikoku headquarters for both Asahi Beer and Coke. The fruits and veggies are also said to be wonderful as well. The city doesn't have much to offer in terms of dedicated sightseeing spots, though we did visit a shrine, an eel restaurant, and an onsen (in that order).
My fridge is now stocked with bottles of all shapes and sizes. I'll be drinking Saijo water until 2012 - at which point the world will end.