Bottle holders are on the inside of the doors.

CAUTION
Do not use the bottle holders for containers without caps. The contents may spill when the door is opened or closed.
Cup Holder
Storage CompartmentsMazda 6 Owners Manual: Inspection of sst (deployment tool)
Use the SST (Deployment tool) to deploy a live (undeployed) air bag
module or pre-tensioner seat belt before disposing of it.
Before using the SST (Deployment tool), inspect its operation.
Inspection Procedure
Follow the steps below to verify that the SST (Deployment tool) is
operatin ...
Mazda 6 Owners Manual: Rear door speaker removal/installation
1. Disconnect the negative battery cable.
2. Remove the rear door trim.
3. Remove in the order indicated in the table.
4. Install in the reverse order of removal.
Rear Door Speaker Installation Note
Attach the speaker with the wiring harness placed in the groove of the door
unit panel.
...