Spreadsheets saved as .fods files are rather uncommon, yet accepted in all office suites based on the OpenDocument format.and can be thus saved in other formats, including XLS format from Microsoft Excel. You may download programs like LibreOffice or OpenOffice.org for free so it should be simple enough.
Convert OpenDocument Flat XML spreadsheet file to Microsoft Excel 97 to 2003 workbook.
We have found 2 software records in our database eligible for .fods to .xls file format conversion.
Apple macOS / Mac OS X software - convert fods to xls on OS X
A full-featured set of office applications for Mac OS X
Convert from fods file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned fods to xls. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Multiplatform software - convert fods to xls on any platform
Spreadsheet program from OpenOffice.org productivity suite