If you can link the feature class to the excel table/spreadsheet by a common field (e.g. the spreadsheet values referencing a matching ObjectID in the feature class), a Join might be a good option. Add Join (Data Management)—ArcGIS Pro | Documentation
edit - not an AGOL solution
I'm assuming you mean in a hosted web layer? If that's the case, there's no way to do it "automatically", but there are ways to make it easier.
If your layer is published from a standalone excel file, as in the image above, you can choose to Append to the layer by re-uploading the same file. You can also overwrite the entire file, but if your source data has a unique identifier field, the Append option can be used to maintain existing features.
If you have the option, consider adding your data from a cloud drive, such as Google Drive or Microsoft OneDrive. The adding process works the same as when adding from a standalone layer. The key difference here is that the update process just looks for that same file in your cloud drive, and you don't have to maintain an offline copy.
This method is great if you're collaborating with other users on the data, or want to take advantage of the built-in versioning and sharing options of the cloud drive of your choice.
Finally, whichever option you choose, you can use the Python API to schedule a script which runs the append or overwrite function at regular intervals, thus making the hosted layer as close to a "live" copy of the Excel sheet as is feasible.