The normal route into Sudak is via Simferopol International Airport, the main airport on the Crimean Peninsula. There are 2 flights a week from Frankfurt. Another option is to go via Tallinn or Riga, now well served by no-frills airlines, and take a flight from there e.g. on Air Baltic or Estonian Air. Of course there are also flights from Moscow, Saint Petersburg and Kiev, as well as some other major cities in the former Soviet Union.
There is a ferry from Varna, Bulgaria served by charter airlines, and WizzAir flies to nearby Bourgas to Yalta sometimes subject to unpredictable cancellation. It is easy to take a bus, minibus or taxi from either Simferopol or Yalta, although it helps if you can speak Russian.
If you have the time to spare, trains also run into Simferopol from major cities in Russia and the Ukraine. A cheaper option than flying.