Of course they have cutesy nicknames for each other.
How could they not?
Cyclonus uses his nickname for Galvs more sparingly, usually when they're alone and close, he likes letting it slip during these more intimate moments as he's not one for huge external displays of emotion.
Galvatron ABSOLUTELY calls him Honeybun ALL THE TIME, Galvatron simply cannot stop the outpour of love for his precious widdle wuv-bun! He absolutely 'smooshes' Cyclonus's face and pinches his darling cheeks as he does it too because GOSH DANGIT BBY YOU ARE MY CUTIE HONEYBUN AND I McHECKIN LOVE YOU OKAY I CAN'T CONTAIN IT IN MY COMPARATIVELY FEEBLE BODY.