not hold (your) liquor

to not be able to drink alcohol without showing any effects.

Scott didn't hold his liquor very well — he'd either fall asleep or sit silently and sadly after a couple of drinks.

Usage notes: the opposite meaning is expressed by hold your liquor:

Now there's a gang that can hold their liquor!

• take your time
• talk a blue streak
• talk back
• talk back to
• talk back to someone
• talk dirty
• talk down
• talk down something
• talk down to
• talk down to someone
• talked out
• talk in riddles
• talk into
• talk into something
• talk of the devil
• talk out
• talk out of
• talk out of arse
• talk out of both sides of mouth
• talk out of both sides of your mouth
• talk out of something
• talk out of the back of head
• talk out of the back of your head
• talk out of turn
• talk out of your arse