How do I get a Diet Pepsi stain out of my cloth heated car seat?

Consult your owners manual, or look up on line. I would blot it with clean water, let dry.

You need an almost dry cloth or soft sponge to wipe as much of the drink off as you can. Rinse the cloth and wring it out. Spray the cloth with a little fabric cleaner like Spray and Wash. Clean the stain again, rubbing the spray into the fabric. Let that dry. Come back again with an almost dry cloth and water. This should clean most of the stain. Repeat if needed, and let dry thoroughly. Use Scotch Guard spray or another fabric protector. (This is safe for heated seats.) Use a skippy cup from now own. 😀 Best wishes 😇

Blot till dry (if not already), and use an upholstery foam cleaner to prevent oversaturating with water. Following directions on can...most likely you will need to wipe with a slightly damp cloth and let dry, or vacuum.

Thank You!