Why not purchase a Rubbermaid Carry Caddy for $24.99.  If you are remotely into detailing or perhaps for non-detailing bottles this will add convenience to your life traveling or working on your car in general.  With detailing bags often being more expensive and less practical than a product like this that serves a specific use case, there is a reason for having a product like this.

It is a plastic product, but it does feel premium to the touch.  Functionally light weight, meaning it is not heavy but appears durable.  It can hold wider based 32-ounce bottles.  You can fit 8 bottles in the Rubbermaid Carry Caddy. The dimensions are 15″ x 11″ x 8″, not taking up any more space than necessary.

I went on a trip down the interstate, with the Rubbermaid Carry Caddy in my trunk.  Nothing tipped or spilled, safe storage!

My only real criticism, albeit an unrealistic expectation, thinner bottles are not going to fit as securely as some of the thicker bottles pictured. Bracketing those bottles with securely fitted bottles or filling up the Carry Caddy makes this a non-issue.

Overall, the Rubbermaid Carry Caddy is a great addition to your detailing setup!