GNIRS L-band spectra of 12 red sources in the CMZ. The observed spectra (red) are vertically offset for clarity and approximately ordered by increasing strength of the broad H₂O ice absorption band centred at 3 μm. To illustrate the varying depth of this feature, the best-fit IRTF/SpeX M5.5III template spectrum (Rayner et al. 2009) is shown in green for each source. These templates were reddened using the foreground extinction estimate derived from our SED fitting procedure (see Sect. 4.1). Together with the 3 μm ice absorption profile, they reproduce the overall continuum shape and slope of the observed spectra.