"We do not have one liter beer."
Translation:Nós não temos cerveja de um litro.
If it's referring to the size of a liter bottle, then it should say "...one-liter beer." Otherwise, it should say "We do not have one liter OF beer" The current phrase is not correct in English. Also the answer given in English includes the word "de" which makes you think "of" should be in there somewhere.
Not just a hyphen but a rearrangement of the words. "We do not have beer in one-liter[s]" but I still cannot imagine leaving out the container aspect (container, bottle, can, glass). "We do not have 1-liter containers of beer" or, "We do not have 1-liter beer containers" or, "We do not have a one-liter sized beer" or, "We do not have a one-liter size of beer."
Or the plural needs to be used: "We do not have one-liter beers."
If duo wants to teach a difference here it should make sure the other language is clear about what is being said. In this case it isn't and it's therefore much more correct to say "Nós não temos um litro de cerveja [como precisa o receite desse prato]."
Duo should not generally expect the most simple and adequate translation on the one hand and then come around with basically wrong examples for the exception or idioms on the other expecting the user to decipher some ill-worded intent.