Applications are usually stored in / data / app, but you can only access this folder if your phone is rooted.
So AFAIK, the only way to do this is to possibly include your apk in the resource folder and then copy it to the SDCard before you can share it. But then the resulting apk cannot be split, because it does not have another apk inside the assets. Therefore, forget about this decision.
The cleanest way is to direct the user to the market.
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