Nikwax has been my choice of cleaning my backpack for over 10 years. Most of the other cleaners out there seem to change the look and feel of your backpack. Nikwax seems to clean the dirt and grime off and returns your backpack to what it felt like new. It does not soften the fabric or adds any fragrance.
In addition to the clean, I also use the waterproofing to return the original waterproofing back. Fair warning and make sure to follow the directions.
Using the tech wash followed by softshell proof will restore your pack and help you remember why you chose it in the first place. Please note, it will not repair the zipper or patch holes.