You place a orange drink in the frig and forget it. The drink now has an off taste and bubbles. What is the?

Question

What is the most likely explanation for the changes in the drink?

Answer 1

Replace is correct.  The drink is fermenting ('rotting'). Biochemical reactions are creating the bubbles. Eventually, the carbonation will stop and it will be horrendously sour.  I do not advise drinking this.

Answer 2

Fermentation.  Prison inmates try to keep fruit and juice for this reason.

Answer 3

You mean making popsickles???   Made them all the time when we were kids...