Hi there,
there is a new service around. The Sentinel-2 Global Mosaic (S2GM) service.
It is a component of the Copernicus Global Land Service providing composites from time-series of Sentinel-2 surface reflectance observations. S2GM comprises best representative pixels in three spatial resolutions and from different compositing periods ranging from one day to one year on a European scale currently and globally next year.
Have a look if you are interested in the data.
The output formats of S2GM are supported by SNAP if you install the corresponding plugin, which is available via the plugin manager.