Dutch courage 
noun [mass noun]
Strength or confidence gained from drinking alcohol: I’ll have a couple of drinks to give me Dutch courage...
- We all know drink gives us all Dutch courage and if ever bravery medals should be awarded then give it to a drunk.
- For those of you who have yet to give the concept a go, the idea is simple and not in the slightest bit scary, especially after a drink or two for Dutch courage.
- Joe made a hasty retreat to the local alehouse in an attempt to gain Dutch courage prior to breaking the news to Linda.