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: Contact Authorized Mazda Dealer and Have Vehicle Inspected
If any of the following warning lights or the indicator light turns on/flashes,
the system may have a malfunction. Contact an Authorized Mazda Dealer to have your
vehicle inspected.
...
Mazda 6 Owners Manual: Rear wiper motor removal/installation
1. Disconnect the negative battery cable.
2. Remove the rear wiper arm and blade. (See REAR WIPER ARM AND BLADE
REMOVAL/INSTALLATION.)
3. Remove the liftgate lower trim. (See LIFTGATE LOWER TRIM
REMOVAL/INSTALLATION)
4. Remove in the order indicated in the table.
5. Install in the revers ...