JustCloud allows you to download a desktop client after you sign up for an account and give you 14 days to try the service for free. Their stated storage space is the lower of 50MB or 50 files, and their sync folder gives you 15MB storage and sharing, but the storage space increases with every sync, share and backup. The free trial comes with a range of features included in the paid packages as well, such as adjustable backup settings.
Free Trial for 14 Days with 50MB Storage
Try JustCloud and all of its features on your devices free of charge for 14 days with a free trial account offering 50MB of storage space and 15MB data syncing space.