The extension FODG identifies files that contain a 2D vector drawing in the uncompressed format of the OpenDocument standard.
The FODG format is part of the Open Document for Office Application Standard, also known as OpenDocument. Originally developed by Sun Microsystems and based on XML, the standard has been defined and developed by the Organization for the Advancement of Structured Information Standards (OASIS).
The uncompressed form as a single XML with the extension FODG is not very common. The ZIP-compressed variant with the extension odg is the standard.
The files, because they are pure XML can be read with any text editor, but you will not get the correctly formatted document.