We present REQreate, a tool to generate instances for on-demand transportation problems. Such problems consist of optimizing the routes of vehicles according to passengers' demand for transportation under space and time restrictions (requests). REQreate is flexible and can be configured to generate instances for a large number of problems in this problem class. In this paper, we demonstrate this by generating instances for the Dial-a-Ride Problem (DARP) and On-demand Bus Routing Problem (ODBRP). In most of the literature, researchers either test their algorithms with instances based on artificial networks or perform real-life case studies on instances derived from a specific city or region. Furthermore, locations of requests for on-demand transportation problems are mostly randomly chosen according to a uniform distribution. The aim of REQreate is to overcome these non-realistic and overfitting shortcomings. Rather than relying on either artificial or limited data, we retrieve real-world street networks from OpenStreetMaps (OSM). To the best of our knowledge, this is the first tool to make use of real-life networks to generate instances for an extensive catalogue of existing and upcoming on-demand transportation problems. Additionally, we present a simple method that can be embedded in the instance generation process to produce distinct urban mobility patterns. We perform an analysis with real life datasets reported by rideshare companies and compare them with properties of synthetic instances generated with REQreate. Another contribution of this work is the introduction of the concept of instance similarity that serves as support to create diverse benchmark sets, in addition to properties (size, dynamism, urgency and geographic dispersion) that could be used to comprehend what affects the performance of algorithms.