Can you re-ferment non alcoholic beer by adding yeast and sugar?

Adding yeast and sugar to non-alcoholic beer has the potential to trigger fermentation and produce alcohol, though it may not fully revert it back to the same level of alcohol content as regular beer. Here are the steps you could take to attempt re-fermentation:

1. Choose Non-Alcoholic Beer: Select a high-quality non-alcoholic beer that contains fermentable sugars (likely labeled "less than 0.5% ABV" or "near beer").

2. Sanitize Equipment: Ensure that all equipment used for fermentation is thoroughly sanitized to avoid contamination.

3. Prepare Yeast: Rehydrate active dry yeast according to the manufacturer's instructions by mixing it with warm water (check the yeast package for specific temperatures and proportions).

4. Boil Solution: Prepare a simple syrup solution by combining equal parts sugar and water in a saucepan, heat it until the sugar dissolves. Cool it down to a suitable temperature for adding the yeast (typically around 75°F - 85°F).

5. Combine Yeast and Sugar: Once the syrup solution has cooled, add the rehydrated yeast and mix it thoroughly. This solution will serve as the fermentation starter.

6. Add to Non-Alcoholic Beer: Pour the fermentation starter solution into the non-alcoholic beer, ensuring it mixes well. Stir gently to evenly distribute the yeast and sugar.

7. Seal Container: Transfer the mixture to a clean and sanitized fermentation vessel and seal it tightly to create an anaerobic environment. Consider a carboy with an airlock to release CO2 while preventing air from entering.

8. Temperature Control: Place the fermentation vessel in a warm location, typically around 68-72°F (18-22°C), to encourage yeast activity.

9. Wait and Monitor: Depending on the yeast type, it could take a few days to a couple of weeks for fermentation to occur. Keep a close eye on the container.

10. Bottle and Condition: Once fermentation appears complete (no more signs of bubbles forming), you can bottle the mixture for further conditioning. Leave it undisturbed in a cool location for another 1-2 weeks.

11. Check Carbonation: After conditioning, carefully open a bottle to check for carbonation. If it carbonates to your liking, you can enjoy the re-fermented non-alcoholic beer.

Note that the resulting beverage may only contain a slight amount of alcohol, not reaching the same level as traditional beer. Additionally, the taste may differ from the original non-alcoholic beer due to the additional fermentation process. It's important to approach this process carefully and be aware of local regulations regarding homebrewing.