Spartan: This is the common penal Juicer. He is an otherwise normal human male, either heterosexual or bisexual, who committed an offense and got caught. (Or got framed, but we're talking Official Dogma here.) He is a trained soldier, and the specific form of Juicer he becomes depends upon that training; most are baseline, a few are Phaeton (pilot) types, with others being rare or non-existent. These guys get used like marines; they get sent first where the resistance is hardest, and they are expected to succeed or die trying- those that retreat do get shot by their (not-Juicer) officers. Very few ascend into the Immortals. Their CO is always "Leonidas", and they come in 300-man units; amongst the Inner Elite, this is considered hilariously funny.
Theban: The Inner Elite has little love for homosexuals. Thanks to DNA testing, male homosexuals are identified early and then tracked into training as a Juicer upon draft age; neither they nor their families are ever told that this is anything other than a high honor. They are not mistreated, but--as with their namesakes--are encouraged to find love within the ranks. If those Spartans are the dogmeat sent into the grinder, Thebans are glorious soldiers sent to do Very Important Things that nevertheless are usually certain death such as hold the line during retreats, make diversionary assaults against hard points or take on enemy elites and tie them down so artillery can tear them up. (The artillery commanders aren't told to be precise, by the way.) Most of the Immortals come from these units. These also come 300 at a time; this too is often thought of as a hilarious joke.
Gorgon: The Inner Elite has no need of women that can't breed (not won't; they send those women elsewhere), and are too ugly to use as spies (not too plain; again, those women get sent elsewhere- we mean fugly). These women are the rarest of the Coalition Juicers, are always of the baseline model, and operate as three-man teams. They aren't used in military operations on the battlefield. They're used strictly as deniable killers by Intelligence. The team leader, usually the most personable of the trio, is "Medusa"; their handler is always "The Eye". The Inner Elite snicker like brats over this also. Gorgons that ascend into the Immortals are rare.