We identify an opportunity to share data among mobile apps hosted in the cloud, thus helping users improve their mobile experience, while resulting in cost savings for the cloud provider. In this work, we propose a platform for sharing data among mobile apps hosted in the cloud. A "sharing" is specified by a triple consisting of: (a) a set of data sources to be shared, (b) a set of specified transformations on the shared data, and (c) a staleness (freshness) requirement on the shared data. The platform addresses the following two main challenges: What sharings to admit into the system under a set of specified constraints, how to implement a sharing at a low cost while maintaining the desired level of staleness. We show that reductions in costs are achievable by exploiting the commonalities between the different sharings in the platform. Experimental evaluation is performed with a cloud platform containing 25 sharings among mobile apps with realistic datasets containing user, social, location and checkin data. Our platform is able to maintain the sharings with very few violations, even under a very high update rate. Our results show that our method results in a cost savings of over 35% for the cloud provider, while enabling an improved mobile experience for users.