#!/bin/bash
s='setting01 = 0          # Comment for setting 01
setting02 = 1          # Comment for setting 02
setting03 = "./folder" # Comment for setting 03
setting04 = "string"   # Comment for setting 04
setting05 = 1          # Comment for setting 05'

sed -E 's/(setting01 = )("[^"]*"|[^[:space:]]+)/\11/g'  <<< "$s"