You cannot send a "fake" Bitcoin transaction that you have. Majority of the network runs the reference client which also follows the protocol rules. With that in mind, the nodes will reject and refuse to propagate any transaction that doesn't follow its rules. The main rules is that the transaction must have a valid signature which would provide the proof that the UTXOs are authorised to be spent. In addition, its also not possible to fabricate a transaction with fake inputs since the inputs must be in the UTXO list of the individual nodes.