The Sansa Clip / Clip+ devices are remarkably resilient. A good drying out should be all you need, mixed in with a little patience.
Sweat contains salts, which form conductive deposits on the circuitry. This does complicate things a little bit, but a bath in distilled water actually does help (though the process takes longer). In the fire service, we had a distilled-water ultrasonic bath for those inevitable radio drenchings that would happen on occasion. $1500-plus pacsets don’t mix well with water.
First and foremost, don’t attempt to turn on the device. Place it in a small beg with dry rice, common grocery store rice. It has an amazing affinity for moisture absorption and will accelerate the drying process nicely.
Place the bag on a warm and dry location. Indirect sunlight, like you’ll find on a window sill, is great. DO NOT use a hair dryer or other heating method, as the internal lithium battery will not like the heat!
After it has had a few days to dry, plug in the device, and see if it comes to life. The charging process will help as well, as the process involves a little internal heat as the battery charges.