Depending on the temperature of the room and the amount of yeast that made it into the bottle, your ginger beer can take up to 10 days to fully ferment and carbonate. Check on the plastic bottle after 5 days. If it is firm, the soda is likely carbonated. Open the bottle and give it a taste.
Brewing your own alcoholic ginger beer is no big deal! If you like the fiery taste of ginger, you'll love this homemade fermented drink. Its alcohol content is similar to that of a beer, which is usually between 3 and 5%.