On August 14, 2019, LIGO and Virgo detected a black hole–neutron star merger, one of the first of its kind. An extensive search for an optical counterpart of this event was undertaken by the Dark Energy Survey Gravitational Wave Collaboration using DECam on the CTIO Blanco 4m telescope. A number of candidates were found and target of opportunity interrupts were issued over 8 nights to observe the candidates using the SOAR Goodman Spectrograph. We describe the process of observing, the analysis of the spectra and our conclusions that none of the candidates corresponded to the black hole-neutron star merger but all were instead other transient events. We also present our process for spectroscopically typing kilonova candidates using the SOAR Goodman spectrograph and describe software packages that we have developed for this purpose.