Answer : The main reason is because of fermentation the orange drink has off taste and bubbles in it.
Explanation : When the orange drink was opened and kept in the refrigerator it got exposed to the atmospheric micro-organisnms, which when started to decompose the drink generated the carbon dioxide bubbles and gave it a bad taste. The decomposed drink may be have turned into vinegar or some other compound which gave it a bad taste after the fermentation process.
