Carbonation can speed up alcohol absorption. What this means is that when alcohol is mixed with soda or other bubbly substances speeds up the passage of the alcohol from the stomach to the small intestines, which then causes the speedy rate of absorption.
There are also other factors that affect alcohol absorption in the body and these are: gender, body weight, stress, medication, health concerns, and the way you drink alcohol (e.g. chugging or sipping). Due to these reasons, each individual has a different variation of intoxication and level of tolerance with alcoholic beverages.
Self-serving roles are those help that you can offer to your clients, it may refer to how to establish trust and rapport with you clients. In might not be written in any book on how to apply this but it your own self that can serve these roles to your clients.