If I put an unopened bottle of soda water in the refrigerator and decide two weeks later that there is not enough room so I store it in a cabinet outside the refrigerator, will it lose its bubbly taste and carbon dioxide?
If it's unopened it will stay perfectly fine, cold or warm, until the Best Before date printed on it.
It doesn't need refrigerating until opened - unless, of course, you want to drink it cold ;)
The CO2 would have to actually leave the bottle for the drink to go flat, and that's no more likely than when you store it at constant temperature. I often do this anyway as I'm short of fridge space and don't drink many fizzy drinks, and I've never had a problem