"I am putting my sandwich in the trash can."
Translation:Je mets mon sandwich à la poubelle.
After reading several explanations: à la poubelle is the Generic Expression used most often by French. The difference seems very subtle - put it in the trash; throw it; place it inside the trash can. Look up lancer vs jeter :: to toss vs to throw. If you can offer other suggestions they may help with this understanding.
I thought dans should be part of the sentence since it's putting the sandwich in the trash can
I put "dans la poubelle" and it was marked correct, so it could be part of the sentence.