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If soda has spilled inside your car's plastic cup holders, buy a cleaner specify formulated for the plastic insides of your car. Spray this cleaner into the cup holders, then scrub at the soda stain with a toothbrush. After scrubbing, stuff paper towels or a clean rag into the cup holder and wipe away the cleaner and stain. If you can't find a car cleaner, use an all-purpose cleaning spray, a 1/1 solution of white vinegar and water, or soapy water. If the stain is particularly large or old, you may have to repeat this process several times to completely remove the stain. Use baby wipes or cleaning wipes to spot clean the inside of sticky cup holders. This is a good step to take if you have already done an initial cleaning but are left with individual trouble spots in your cup holders. To clean, rub the baby wipe or cleaning wipe on the stain until it has been rubbed away. If you have spilled your soda onto the plastic sidings of the car or the car door, use ammonia-free glass cleaner to remove the stain. Spray a few sprays of the glass cleaner onto a clean rag or paper towel, then wipe away the stain. Don't use glass cleaner with ammonia, as this can bleach the plastic.

Summary:
Use cleaning spray and a toothbrush to clean cup holders. Spot clean the cup holders with a baby wipe. Use glass cleaner to clean plastic car sidings.