Hello, Anton!
The cheapest way is to use solution based on emails sending...
for example: http://shareo.4team.biz/?pcode=607180190pwkkd3

But if you would like to avoid email sharing you can use service and
synch via someones server
for example this one:

www.outshare.com/

I would suggest the first one - cheaper and more stable... but it
depends on situation

Regards, Julia