How to sort using my custom field?

This custom field is saved in comment meta? Same concept applies to post meta anyway. Set the query’s “orderby” arg to either “meta_value” or “meta_value_num”. Also set the query’s “meta_key” arg to that of your field’s key name. You do not need a “meta_value” arg (not to be confused with the “orderby” value you set). You would set a “meta_value” arg only if you want to constrain the query results to comments with that value.

If you need to constrain the query by other meta data besides the one you’re ordering by, use the “meta_query” arg.
https://developer.wordpress.org/reference/classes/WP_Comment_Query/__construct/