can you list the ways to join values on a sql query twice?

You would just join twice:

select c.*, f1.fuel_label, f2.fuel_label as secondary_fuel_label
from cars c left join
     fuel_types f1
     on c.fuel_id = f1.fuel_id left join
     fuel_types f2
     on c.fuel_id = f1.secondary_fuel_id ;

The key point here is to use table aliases, so you can distinguish between the two table references to fuel_types.

Note that this uses left join to be sure that rows are returned even if one of the ids are missing.