SPANGLISH ALERT: WE NEED TO DO THAT "YES OR YES"
Although most Spanish people know that "yes or yes" (si o si) can and should not be used in English, for many no other expression comes to mind so they are left wondering what to say.
To be honest, there is no real expression in English is that is quite as nice as "si o si" but the most obvious translation is "no matter what" or "come what may" (less commonly used). So an example: "We need to do the homework, no matter what".
Hope that helps!
Soy el director de Daniel Smith + Partners. Tengo más de 15 años de experiencia enseñando inglés a españoles.