Generating an unsigned IPA iOS application

The easiest way is to build on the command line.

    /usr/bin/xcodebuild -scheme MYSCHEME -workspace MYWORKSPACE.xcworkspace   
    -configuration Release clean archive -archivePath "build/APPNAME.xcarchive" 
    CODE_SIGN_IDENTITY="" CODE_SIGNING_REQUIRED=NO CODE_SIGNING_ALLOWED=NO

Once I copy it from a blog. The steps are as follow:

Build unsigned .ipa without Developer Account on Xcode 5

To Disable Code Signing:

1.1 GoTo /Applications then right click Xcode.app and click "Show Package Contents"

1.2 GoTo Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS7.0.sdk/ and copy the file SDKSettings.plist to desktop

1.3 Open the file copied SDKSettings.plist. Under "DefaultProperties" ==> "dict" find CODE_SIGNING_REQUIRED and change its value from YES to NO. Save the file

1.4 Copy this modified SDKSettings.plist file back to Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS7.0.sdk/ replacing the orginal file [YOU MAY SAVE THE ORIGINAL FILE AS BACKUP] Do the required AUTHENTICATION AS REQUIRED

1.5 Restart Xcode and open your runnable xcode project

1.6 In Project Navigator select your project and open Build Settings section of your porject and Select All sub-heading.

1.7 Under Code Signing find Code Signing Identity and for both Debug and Release modes set Any iOS SDK to Don't Code Sign.

To make an IPA:

2.1 In Xcode, goto Product and click Archive

2.2 7th step will build you project and creat an Archive. After the completion of the process, new window Organize - Archive will be opened. In the list of this window you can see your project. Right click project and click Show in Finder which will reveal *.xcarchive file

2.3 Right click the *.xcarchive file and click Show Package Contents and goto Products => Applications where you will see an app file with the name of your project "projectname".app

2.4 Open iTunes change view to Apps and drag the app file "projectname".app into the iTunes.

2.5 Right Click your app, click Show in Finder. There you will have you .ipa file.

Important Notes :

3.1 In Step 2.1, if the Archive menu is disabled this is most likely because the a simulator option is currently selected as the run target in the Xcode toolbar. Changing this menu either to a connected device, or the generic iOS Device target option should enable the Archive option in Product menu.

3.2 You will also need to install AppSync in your iPhone via Cydia.