I don’t know!!!!
The 4-way stop intersection does not exist in the motor vehicle act, so we must use our best judgment and be cautious and courteous at 4-way stops, as the rules for stop signs indicate that you not proceed until you know it is safe (I know, this is not very helpful information).
What I would recommend if this happens to you frequently is to control the speed of your vehicle so that you don’t stop at the exact same time as the other vehicles. If you see 3 other vehicles approaching, simply slow down earlier than the other vehicles and stop after them; it is much easier to figure out who goes first if there are only 3 cars.
As always, make a very obvious and clear stop – avoid rolling up to the stop sign so slowly that the other drivers aren’t sure when exactly you stopped. Don’t give yourself whiplash, but do make it obvious; this can help as well.
Also, look at the direction the drivers say they want to go. If all 4 cars want to go straight, that is a much larger problem than if they all want to turn right.
The most obvious answer to this question is to go in order of engine size: Ferrari, Corvette, Nissan 370Z, then Kia (no offence) for example. You could also go in order of colour. Since red cars go faster than others, red should always go first, then yellow, then white, then black.