A small 1/8" hole or something isn't going to seriously effect the sound characteristics of the mufflerdrilling a hole in it will make it loose its ability to control sound waves coming out of the engine.
I would leave it be. No drain is needed in the muffler. The amount of water it will see is very little. Most of it will evaporate due to the heat cycles before it would even turn to a solid.Does stock muffler has drainhole on 06 corolla le?
Should I drill a hole to let water drain if there isn't one? Will it make a louder exhaust?