A glass of gin and tonic
Opening Room-Temperature Tonic Water Is A Huge Mistake
The key to a refreshing gin and tonic is the carbonation of the tonic water. The bubbles add a crisp element to the drink and accentuate the botanical notes in the gin.
This is why opening and using tonic water while it's at room temperature is a big mistake. It loses carbonation much faster than chilled tonic water, leading to lackluster results.
Carbon dioxide, which is responsible for carbonation, escapes more readily in warmer conditions. The tonic water loses its effervescence, leading to flat, watered-down drinks.
For the optimal drinking experience, always use tonic water that has been refrigerated for at least 30 minutes. Serving it over cracked ice also ups the chilliness for more refreshment.