  We study finite volume effects within the Polyakov loop Nambu-Jona-Lasinio
model for two light and one heavy quarks at vanishing baryon chemical potential
and finite temperatures. We include three different Polyakov loop potentials
and ensure that the predictions of our effective model in bulk are compatible
with lattice QCD results. Finite size effects are taken into account by means
of the Multiple Reflection Expansion formalism. We analyze several
thermodynamic quantities including the interaction measure, the speed of sound,
the surface tension, and the curvature energy and find that they are sensitive
to finite volume effects, specially for systems with radii below $\sim 10$ fm
and temperatures around the crossover one. For all sizes, the system undergoes
a smooth crossover. The chiral critical temperature decreases by around $5 \%$
and the deconfinement temperature by less than a $2 \%$ when the radius goes
from infinity to 3 fm. Thus, as the drop's size decreases, both temperatures
become closer. The surface tension is dominated by the contribution of strange
quarks and the curvature energy by $u$ and $d$ quarks. At large temperatures
both quantities grow proportionally to $T^{3/2}$ but saturate to a constant
value at low $T$.
