I accidentally put a USB to Lightning cable in the washer and dryer. The cable is mostly ok, but the plastic at the lightning end got a little warped. Am I risking anything by trying to connect a device with it? I'm reluctant to damage an iPhone, but at the same time, those cables aren't cheap.
I would caution you to consider that all Lightning cables have small chips (basically a little computer inside them) to control charging as well as signaling. It's not as damaging as putting a phone through the wash, but depending on the age of the cable and if it's physically intact - water could easily compromise the electronics in the connector. Especially when it's warped by the heat of the dryer or otherwise compromised physically.
We have confirmed that the Lightning cable does have four chips embedded in it, plus some passive devices. Two of these chips are very simple (only a couple of transistors), and the third is an NXP NX20P3. However, the fourth and arguably most interesting of these is the TI chip.
Details of the chips are from http://www.chipworks.com/about-chipworks/overview/blog/inside-apple-lightning-cable
One trip on a new cable is probably low risk of damaging the phone if you use it, buy if the cable connector is cracked or that water damage causes corrosion, some time down the line that cable will fail. I'm sure it's designed to fail in a safe mode, but this isn't a situation where you have wires that can dry out harmlessly as you would expect if you had headphones that go through the wash or an older 30 pin cable design that was simply wire and plastic.
If you let the connectors dry for a day over the heating you are save.
If a cable gets wet (and nothing else happens in a washing machine) it will soak with water (the detergent improves that). A wet cable may produce short circuits but not really in that kind of connector. It works at 5 Volt levels and that is much too weak to produce harm. So what you would eventually notice is that electronic communication over such a cable would not work.
Luckily water can evaporate over time (faster with higher temperatures). So after a day over the heating latest it's ok. If after that it's still not working - buy a new one :-)