How to find the alcohol content of a probiotic liquid? Probiotics are microorganisms that are believed to provide health benefits when consumed. Water Kefir is one such probiotic drink. This has blend of bacteria, yeast (BY), sugar water and the result of action of BY on sugar water. There is alcohol. One of my problem is to find out the alcohol content in the solution. Less expensive, simpler methods/protocols are much appreciated.
Complex instrumental analytics (HPLC, photometry using a $\ce{NAD+/\,NADH}$ testing kit, etc.) is out of question.

In principle, the most simple approach would be the use of a hydrometer to measure the density before and after fermentation.