"Heb jij tandenborstels?"
Translation:Do you have toothbrushes?
This sentence isn't correct in English without "any". Mostly because you are probably only looking for one toothbrush.
It does sound more natural to include "any" or "a", but it should be exceptable because you can also say "Do you have cows/dogs/eyes?" and it's correct.
but when you ask for cows/dogs/eyes you could just as easily be looking for multiple cows, dogs or eyes. You definitely cant use "a toothbrushes" but while i agree without "any" it is technically good English it leaves out the consideration of the subject, if you only have one toothbrush in a shop it's probably not the place you want to be buying toothbrushes, but most of the time you are only looking for one.
Also, there is no x in acceptable.
Yh, the most likely scenario i can think of where you would use this in the plural form, would be if you went into a shop and asked them if they had toothbrushes, though more likely you would ask them if they sell toothbrushes