Android - Equivalent of CTRL + C (break) in android console

Vol Down + C is functionally equivalent to Ctrl + C.

There may be a way to send the modifier keys through the terminal app, however I have never used that app so I can't say. On Terminal Emulator you can long press the screen and send the control key from the pop up menu.

Also you could install Hackers Keyboard which includes a full desktop keyboard including control and alt keys.