Learn Dutch: Deze container is immers alleen voor blik. - This container is only for cans, after all.

Immers is used to justify a statement using information that the speaker assumes the listener already knows. It translates roughly to 'after all' or 'as you know.' Here, the speaker is reminding someone that the container is for cans, likely because the person was about to throw the wrong trash in it.

Why is immers placed right after the verb is?

As an adverb of consensus, immers typically goes in the middle field of the sentence, which is right after the finite verb in a main clause. It comes before specific details like alleen voor blik.

The English translation says 'cans', but isn't blik singular?

Yes, blik literally means 'tin' as a material. In Dutch recycling terminology, you use the singular, uncountable material name to refer to the category of waste, just like we say 'glass' or 'paper' in English.

Could I say dit container instead of deze container?

No, because container is a de-word. For de-words, you must use deze (this) or die (that). You only use dit and dat for het-words.