We discuss an application of the well-known Multiplicative Weights Update (MWU) algorithm to non-convex and mixed-integer nonlinear programming. We present applications to: (a) the distance geometry problem, which arises in the positioning of mobile sensors and in protein conformation; (b) a hydro unit commitment problem arising in the energy industry, and (c) a class of Markowitz' portfolio selection problems. The interest of the MWU with respect to one of its closest competitors (classic Multi-Start) is that it provides a relative approximation guarantee on a certain quality measure of the solution.