No, just balls of hydrogen that condensed into a sphere due to gravity trying to pull all of its mass to its center causing it to become a sphere. A flat sun theory works even less because while a flat plant is possible, a flat sun is not. The hydrogen it is formed of isn't strong enough to withstand gravity. Although, even if you did, it wouldn't be a star because the force that is stopping it from collapsing would have the extra effect of preventing it from growing hot and obtaining the pressure to commit fusion... and with no fusion it's just a really, really, really big planet.
Or, the sun is just a big ol' mirror and all the light that earth creates is just reflected back at us. Because that makes as much sense as the flat earth theories.
NEW THEORY: FLAT SUN CREATED BY ITALIANS?