Here are a couple of options, keeping in mind that some flexibility is necessary:
Option 1 (Prioritizing Phonetics):
* Athens: Αθήνς (Athins) - This is a reasonably close phonetic representation, using the existing Greek name for Athens.
* Frudaker: Φρουτάκηρ (Froutakēr) - This is a phonetic approximation. The "Fr" is represented by Φρ (Fr), "ud" by ου (ou), "ak" by ακ (ak), and "er" by ēr (ηρ). It's a plausible sounding Greek name, but doesn't visually resemble the original.
Option 2 (Prioritizing Visual Similarity):
This is more difficult and less satisfactory phonetically. We'd need to find Greek letters that *look* somewhat similar, even if the pronunciation differs. This would likely result in a name that sounds quite foreign to a Greek speaker. It's not recommended unless purely for stylistic purposes.
Therefore, Αθήνς Φρουτάκηρ (Athins Froutakēr) is probably the most practical and understandable transliteration, albeit not a perfect one. A Greek person might still find it slightly unusual.