No problem:

~$ls -l /bin/bash
-r-xr-xr-x 1 root wheel 1296704 1 Jan 2020 /bin/bash

~$/bin/bash -l -c "which afni"
-------- freesurfer-Darwin-OSX-stable-pub-v6.0.0-2beb96c --------
Setting up environment for FreeSurfer/FS-FAST (and FSL)
FREESURFER_HOME /Applications/freesurfer
FSFAST_HOME /Applications/freesurfer/fsfast
FSF_OUTPUT_FORMAT nii.gz
SUBJECTS_DIR /Applications/freesurfer/subjects
MNI_DIR /Applications/freesurfer/mni
FSL_DIR /usr/local/fsl

~$echo $?
0