What you should not do:
Experts have for years pointed out that’s a bad idea – and now Apple is officially warning users not to do it.
“Don’t put your iPhone in a bag of rice. Doing so could allow small particles of rice to damage your iPhone,” the company says in a recent support note spotted by Macworld. Along with the risk of damage, testing has suggested uncooked rice is not particularly effective at drying the device.
What you should do:
If your phone isn’t functioning at all, turn it off right away and don’t press any buttons. The next steps depend on your specific circumstances, but broadly speaking: dry it with a towel and put it in an airtight container packed with silica packets if you have them. Don’t charge it until you’re sure it’s dry.
How exactly do small particles of rice damage a cell phone? I can't think of any realistic way for that to happen
The same way the water does; by causing shorts.
Except that rice is an insulator and has no physical way to get to anything electrical to begin with.
Rice absorbs moisture. The moisture might make it more conductive.