Ethanol solutions are present in many industries, including the beverage, medical, and fuel industries. While electrical methods for measuring the ethanol concentration in solutions are subject to electromagnetic interference, may require large amounts of solution, or take a long time, optical techniques based on fiber optics are immune to electromagnetic interference, are chemically inert, and can deliver signals over long distances with minimal noise. However, fiber optic sensors often require expensive equipment to manufacture, e.g. a CO2 laser for manufacturing Bragg gratings, or expensive photonic crystal fibers, and often are difficult to assemble. In this paper, we propose a coreless-fiber-based Fabry–Pérot sensor that is very easy to manufacture; then, we tested and calibrated it in solutions of n% ethanol in deionized water at temperatures of 23, 21, and 19 ℃ in the range n = 0−15 typical in the wine industry. The manufactured interferometers worked either by shifting the minimum of a valley at a rate of 0.07630 nm/n or by decreasing the intensity of the measured signal (absorption) at a rate of −0.15696 dBm/n in the entire range n = 0−15.