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: Precaution
Vehicles with ABS/TCS
1. The ABS warning light, BRAKE system warning light, TCS indicator light
and/or TCS OFF light illuminate even when the system is normal.
*1 : In cases where the light may illuminate, only when ABS/TCS HU/CM detects
that speed sensor of rear wheel is malfunctioning.
*2 ...
Mazda 6 Owners Manual: Washer Fluid
Inspecting Washer Fluid Level
WARNING
Use only windshield washer fluid or plain water in the reservoir:
Using radiator antifreeze as washer fluid is dangerous. If sprayed on the windshield,
it will dirty the windshield, affect your visibility, and could result in an accident.
Using Washer Flu ...