The paper presents a new approach to developing exposed-core fibers. We designed a new asymmetric structure of suspended core fibers with series of additional air holes in the cladding. Using the standard wet etching method we removed a part of glass, demonstrating that the method allows to open a selected air hole surrounding the suspended core. Such modified of fibers can be used to build sensors and devices dedicated to chemical and biological studies and based on the interaction of light with liquids. We used the developed fiber to develop an interferometric sensor that measures changes in the refractive index with a high accuracy. As a proof of concept, we present the experimental measurement results of the ethanol concentration in water.