I declare the other application in the bootstrap resource roots:
data-sap-ui-resourceroots='{
"own.app": "./",
"other.app": "../App2/"
}'
and I also declare it for the AppCacheBuster:
data-sap-ui-appCacheBuster='["./", "../App2/"]'
Then i would list the module from App2 as a dependency for the module which wants to use it.
sap.ui.define(["other/app/CommonUtils"],
function(CommonUtils) {
CommonUtils.doSomething();
}
That's how I think it should work. Didn't try it yet though.