Ginger beer
Keeping Cold
Keeping any perishable product cold, from food to wine, will help prolong the life of that product. This holds true for ginger beer. Being left in excessive heat can ruin the carbonation, causing the drink to go flat. Because there are generally so many preservatives added to the drink it can be hard for it to actually "go bad." However, if it sits in heat for weeks on end, the taste will change to something totally different.
Restrict Airflow
Air is terrible for the preservation of ginger beer. This is why the caps are sealed on so tight, so air flow is restricted. If you have ever left a carbonated drink out over night you know what will happen to the drink. It will go flat, the taste will be slightly altered, and if it is left out long enough, mold will begin to form on the top. This is exactly what will happen if oxygen is allowed to reach the ginger beer. If properly stored with the cap on, the ginger beer can last several months if not years without the flavor changing. Once the bottle is opened, it is a race against time.
Sunlight
If you have ever wondered why most beers use thick brown glass for their bottles, it is because it best protects it from the sunlight. Rarely will you see a high class, expensive bottle of beer come in a clear bottle. This is because good beer is meant to be stored and aged (some), just like wine, and the sunlight will hinder and ruin the aging process. This holds true for ginger beer. The sunlight will cause a chemical change in the drink, even if it is stored in the cold without oxygen reaching it.