Don't even think of cleaning plugs. If they are platinum plugs, you might damage the plugs. At 25000 km the plugs should be like brand new. Platinum last around 140,000 km to 160,000 km. Even the cheap one should last around atleast 100,000 km.
Check the owners manual if you got one.
One more thing... Cleaning doesnt really do any good. Replacing them after 100,000 km or so is better option.