I de-stunk 2 pairs of mildly smelly gloves with the following method: soak a paper towel full of 90% rubbing alcohol and rub da ish out of the inside of the gloves, then let them air dry. Repeat several times as necessary. Then shove Bounce sheets into the hand compartment, making sure you get them all the way to the fingertips (if that's the problem area). Let them sit overnight in a well-ventilated area (I set my gloves under the HVAC vents, for example). Repeat the whole process after every training session (took about 6 sessions or so for the stink to completely dissipate; may take longer or the stink may never dissipate if it's gotten too bad).
In the future, to avoid stink: 1.) Clean and air dry gloves after every session, 2.) Glove dogs or Bounce sheets inside the gloves after every session while they're air drying, 3.) If you pull your hand out of a stinky focus mitt, buddy's glove, or whatev's, think twice about sticking your hands into your own gloves, 4.) Wash your hands before (wrapping and) sticking your hands into your gloves, 5.) Consider wearing thin cotton work gloves before wrapping your hands (works like a sock in a shoe).