For the water doesn't kill electronics. I loved the look on up and coming electrical engineers' faces when I was borrowing their lab equipment to assemble a $2000 circuit board, and when I was finished I put the board in the sink and scrubbed it a bit. I have never seen such shocked faces.
Water isn't bad for electronics if there's no energy sources. Heck water isn't bad for electronics if there's no free ions, so even running electronics won't worry if you pour distilled water over them. You should be fine.
Washing SD cards should be fine, though. I think the better manufacturers actually test this, although they don't warranty for it. It's a Typical Usage Thing that is simply gonna happen, so they do their best to make sure they'll almost always survive.