How often I can update mobile application on App Store? Can I update every 2-3 days?
Thank you.
Highly unlikely.
Apple's review time for a completely acceptable app update varies from less than 2 days to over 2 weeks, and a developer has no control over that length of time. That will limit the rate of updating any app to Apple's pace. Trying to update more often than this will put your update back at the end of the queue and slow down your approvals, and thus App store releases even more.
Somewhere, maybe a developer's talk, they may have recommended non-critical (for bugs) updates no more often than once per month.
For more frequent updates of content, see Apple's WWDC 2010 video on data driven app design, and consider having the app update certain content from your web site.