guest beer
US /ˈɡest bɪr/
UK /ˈɡest bɪr/

1.
Gastbier
a beer, typically an ale, brewed by a different brewery than the one operating the pub or bar, offered temporarily alongside the regular selection
:
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This week's guest beer is a rich stout from a local microbrewery.
Das Gastbier dieser Woche ist ein kräftiges Stout von einer lokalen Mikrobrauerei.
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They always have an interesting selection of guest beers on tap.
Sie haben immer eine interessante Auswahl an Gastbieren vom Fass.