The Sunshine Balls are large orbs that are able to replicate the sun's rays artificially by giving out a bright light. The radiation also emits some sort of brainwashing powers as the citizens affected by it were rooting happily for Eggman. They needed special towers called "Mirror Towers" in order to keep them functional.
Egg Moon Saga
When the moon was broken in half, Dr. Eggman fixed it by making a robotic contraption, which would slowly move the moon into an orbit in which it blocked the sun's rays. This caused haywire towards most of the planet's citizens. Eggman, in response, developed the Sunshine Balls and distributed through the Eggman Company to provide the people with the much needed light. Unknown to the citizens, he also planned on converting humanity to his side with the Sunshine Balls' brainwashing abilities so there would be minimal resistance from outsiders as he would build his Eggman Empire. The demand for these objects quickly rose within the public until Sonic, who knew Eggman's ulterior motives, proceeded to destroy Mirror Towers which are required to maintain the Sunshine Balls' power.
When Sonic was questioned by his friends and G.U.N for destroying the towers, Sonic unveiled that Eggman was controlling the Egg Moon in order to maintain a permanent solar eclipse and as well as his Sunshine Balls production business, they were all part of a "cheap-get-rich scheme" for Eggman to easily make a profit from the citizens of Station Square, proving Sonic's heroic status once again.