  Fast sausage modes (FSMs) in flare loops have long been invoked to account
for rapid quasi-periodic pulsations (QPPs) with periods of order seconds in
flare lightcurves. However, most theories of FSMs in solar coronal cylinders
assume a perfectly axisymmetric equilibrium, an idealized configuration
apparently far from reality. In particular, it remains to examine whether FSMs
exist in coronal cylinders with fine structures. Working in the framework of
ideal magnetohydrodynamics (MHD), we numerically follow the response to an
axisymmetric perturbation of a coronal cylinder for which a considerable number
of randomly distributed fine structures are superposed on an axisymmetric
background. The parameters for the background component are largely motivated
by the recent IRIS identification of a candidate FSM in Fe XXI 1354
\AA~observations. We find that the composite cylinder rapidly settles to an
oscillatory behavior largely compatible with a canonical trapped FSM. This
happens despite that kink-like motions develop in the fine structures. We
further synthesize the Fe XXI 1354 \AA~emissions, finding that the transverse
Alfv\'en time characterizes the periodicities in the intensity, Doppler shift,
and Doppler width signals. Distinct from the case without fine structuring, a
non-vanishing Doppler shift is seen even at the apex. We conclude that
density-enhanced equilibria need not be strictly axisymmetric to host FSM-like
motions in general, and FSMs remain a candidate interpretation for rapid QPPs
in solar flares.
