Saccharides play crucial roles in a wide variety of biological and psychological processes, and their sensing and control are important in many medical, diagnostic, and therapeutic contexts. We demonstrate here that a novel polymer film can be made to switch between superhydrophobicity and superhydrophilicity on exposure to sugar solutions, due to hydrogen-bonding interactions between thiourea and PBA units in the polymer. This wettability switching is reversible and the contact angle change shows a good linear relationship with the logarithm of the sugar concentration, as well as being distinctly different for different sugars. Furthermore, exposure to the sugar solution is accompanied by a reversible expansion-contraction of the polymer particles. Therefore, this system may find broad applications in other related fields including controllable drug release, microfluidic devices and biochips.