Find where the moisture lives
Empty the cargo area, lift the mat, and smell the mat, backing, seams, carpet, wheel-well trim, and spare-tire well separately. Look for water trails, damp padding, spilled liquids, and blocked drains. Dry the actual source according to the vehicle and product instructions before using fragrance.
New-material odor may fade with ventilation, but persistent or returning odor points to contamination or moisture. Do not seal a damp carpet beneath a waterproof liner and call the problem solved.
Limits
No material, cleaner, humidity, or vehicle was tested. This guide does not promise odor removal or identify mold without inspection.
Sources and related reading
See Also
If you want to move from general advice into actual product choices, start with Cargo Liner for Dogs in an SUV: Containment vs Access, Cargo Tray vs Cargo Mat: Which Floor Protection Fits the Mess?, and Car-Seat Protectors: Waterproofing, Grip, and Child-Seat Fit Tradeoffs.
For a wider picture after the basics, SUV Cargo Liner Adjustable Fitment vs Standard Fit and Best Breathable Car Seat Covers Under $80 for Comfort are the next places to read.