D.N.
I did this when one of my kids was a bed wetter: fill a spray bottle with half white vinegar and half water. Spritz the mattress until just slightly damp. Better to do this early in the day so it is dry by bedtime. If needed, repeat. I never had to do it more than once. Vinegar may have a smell but it is gone when the item is dry. I also use it in my laundry when things get funky.
Updated
I did this when one of my kids was a bed wetter: fill a spray bottle with half white vinegar and half water. Spritz the mattress until just slightly damp. Better to do this early in the day so it is dry by bedtime. If needed, repeat. I never had to do it more than once. Vinegar may have a smell but it is gone when the item is dry. I also use it in my laundry when things get funky.