How do I clean iPhone speakers without damaging them?

Use a really soft brush or a slightly damp cotton swab - no direct water spray. If there's dust buildup, gently run the swab over the speaker slots without forcing anything. Avoid too much alcohol, just enough to clean without leaving moisture inside the device. If there's a lot of stubborn dirt, let the swab sit on it for a few seconds, never try to dig it out with something sharp.

Don't put your phone underwater or use compressed air at high pressure, because that forces water or air inside the device and ruins everything. I had the experience of cleaning mine with a dry cotton swab first (just to get the gross dust out) and then I gently went over it with a cotton swab dampened in distilled water - be really careful not to leave drips, just dampen it. The trick is to make soft circular motions and let it dry completely before using your phone again, and it works well without needing harsh chemicals that can damage the internal components.