The phrase "they don't know how to drink" can be interpreted in different ways, and it doesn't necessarily mean that the person drinks a lot. It could imply various things, such as: Lack of moderation: The person might be suggesting that those individuals don't know how to drink in moderation. This could mean they tend to drink excessively or irresponsibly. Behavior when drinking: It could refer to how individuals behave when they drink. Some people may become overly loud, aggressive, or act inappropriately when they consume alcohol, and the statement might be a commentary on their behavior. Poor choice of drinks: It might also relate to the types of drinks people choose or how they handle different types of alcohol. For example, they might not be aware of their alcohol tolerance or mix drinks in a way that leads to negative effects. Lack of awareness: This phrase could also suggest a lack of awareness about the effects of alcohol, such as not knowing one's limits or not understanding how alcohol can affect the body and mind. Without more context, it's challenging to determine the exact meaning behind the statement. It would be helpful to consider the speaker's tone, the situation in which the statement was made, and any additional information that might shed light on what they meant.

Generally, it would mean they have a low tolerance to alcohol or they just handle themselves very poorly when they are drinking.

He probably means that they drink in a way that causes them to get really drunk. They might drink too quickly, drink on an empty stomach, drink too much, etc.