I don't see how pouring anything down the spark plug hole will help clean the back of the intake valves, which is the real problem.
I would generally doubt the effectiveness any intake valve cleaning that doesn't involve removing the intake manifold.
I would worry how much of whatever you are pouring into your engine will seep down into your oil. I would change your oil immediately after this treatment.
2009 BMW 135i, 6 MT, M Sport, DIY DCI, Cobb AP, Apex 18x8.5+9.5, 235/265 Starspecs