About three weeks ago, I brewed iced coffee in a clean jar; I didn't drink all of it and left it in the refrigerator.
About 1/2 the jar was filled, I then traveled and when I came back, I found in the bottom of the jar something sticky like rubber.
Is this Kombucha ?
I didn't use any kind of "scoby" aka starter, it's just ground coffee with cold water and sugar. This isn't the first time this happened. It smells just as coffee would, nothing bad.