  In the framework of Einstein's gravity, we study the thermodynamic equation
state, $P=P(V,T)$, associated with a flat Friedmann-Lemaitre-Robertson-Walker
(FLRW) universe. In this scenario, we consider the components of the dark
sector as non-interacting fluids that dominate the universe's energy content at
late times. Under these circumstances, the functional structure of the
cosmological coincidence parameter plays a relevant role in admitting
first-order $P-V$ phase transitions; specifically, the dark energy density and
the coincidence parameter must be given in terms of the radius of the apparent
horizon.
