  We study genuine finite density effects in QCD-like theories with
three-dimensional Polyakov-loop effective theories for heavy quarks. These are
derived from the full QCD-like theories by combined strong-coupling and hopping
expansions. In particular, we investigate the cold and dense regimes of phase
diagrams where we expect to find Bose-Einstein-condensation of diquark baryons
or a fermionic first-order liquid-gas transition, depending on the gauge group
of the theory. In two-color QCD, for example, we observe evidence of a
continuous zero-temperature transition to finite diquark density when the quark
chemical potential $\mu$ reaches half the diquark mass, i.e. without binding
energy. In G$_2$-QCD we observe, in addition to this "Silver Blaze" onset of
diquark density, a second transition in the density towards an exponential
increase by roughly $3\mu/T$ corresponding to a finite density of
G$_2$-nucleons.
