I have quite a few of these that don't require a plug any ideas thanks.
unscrew the top; remove any remnant of the original 'gel' ... place a couple of cotton balls in the cup and use drops of an 'essential oil' in a fragrance you like --- citrus, lavender, etc., or use this recipe --- for a gel type fragrance -- https://www.ehow.com/how_4927470_make-solid-air-freshener.html
Hello Jenny! Here is a link that might help!
Jenny,. Put them in inconspicuous place for a fresh odor in you home. Aloha!