For those who want to know “how to fast” on Yom Kippur, fret not. YHWH doesn't expect anyone to put their life in jeopardy!
Those who can do a full fast, stop eating or drinking for 24 hours (except for water). Many choose to do a liquid diet on Yom Kippur, drinking only water and juice, to keep from dehydrating.
For those who are not healthy and/or take lots of medications, it’s probably best to NOT fast at all. Or - at most - give up only one meal during those 24 hours. YHWH won't mind, as long as you try to "deny yourself" of something.
The main thing is to deny yourself of "something" and spend some time in sincere prayer with YHWH, asking forgiveness for anything you did that might have upset Him over the past year. (On Yom Kippur, Bill and I will go to separate rooms to be alone with YHWH and pray.)
Also, if possible, try to reconcile with anyone who hurt you, or whom you might have hurt - but ONLY do it if you know that reconciliation is actually possible, as some relationships are/were toxic and HAD to end. Just forgive them in your heart, and move on. Simply employ your God-given common sense ….