It is a good move definitely that you have taken it out, drained and dried it.
Definitely not a write-off, it can be restored as it contained ~14% alcohol [which would have absorbed any sugary content of the grapes]. [the worse would be coca cola].
You should take out both the lithium battery as cdev has said, and the Bios battery, take out CD rom drive, take out ddram cards. [if removable].
You can used DI water, RO water, distilled water, or Isopropyl alcohol [another alcohol] to wipe clean the board then put the board to dry. Mechanical assisted with hair dryer would be great.
After that, you put it back with the bios battery [don't put lithium, drive, or ddram as yet], plug in the power supply. If you able to see sign of life, then turn it back off, and plug everything in.
If not, then the most is the S5 stage problem and not expensive to repair, far from "write-off".