And they also mention that they use CoinJoin and have temporary wallet functionally, which makes us more confusing whether it's classified as mixer or CoinJoin service.
FAQ Sudoku Wallet:
https://sudokuwallet.io/faqHow to mix my coins?You must add Bitcoins to your deposit address, wait for 3 confirmations then press "Mix my coins!". Using just 1 output address is not anonymous, so your coins will be split random between 2,3 or 4 addresses. You will receive clean coins, pre-mixed with CoinJoin, which haven't any connections with your deposit coins. Then you just should grab private keys, and import in your own main wallet.