Thanks for the advise! That did it. The command is working fine now with the following setup:
currentuser="$(id -u -n)" OPTS=(-q -avz --delete -e 'ssh -i /home/'$currentuser'/.ssh/id_rsa' --rsync-path='sudo rsync') SRC=(/etc/nginx/) RSYNC_CMD=(rsync) for h in balancer0{1..2} ; do DST=$currentuser@$h:/etc/nginx/ $RSYNC_CMD "${OPTS[@]}" ${SRC} ${DST} done