I'm assuming a Sunfire has a hydraulic clutch, since your mechanic was
able to "bleed" it.  A hydraulic clutch basically works like two
syringes - one under your foot and the other at the transmission -
both connected together with a hose.  You push on the one at the
pedal, fluid moves to the other, and the other pushes on the clutch.

The sponginess is from air mixed in with the fluid.  Something must be
leaking.  Your mechanic fixed the symptom without addressing the
problem.  Of course, the leak could have been small enough that he
couldn't see it the first time.

If you can locate the clutch fluid reservoir under the hood, have a
look.  It's probably empty.  The fluid doesn't get used up, so it's
leaking somewhere.

Likely causes are the clutch master cylinder, the clutch slave
cylinder, or the hose.  Frequently it's the slave cylinder because
that lives on the hot end of the system.