I think the weekday table could use some normalisation. You don't really need to list Monday through to Sunday as you already know the date in the concert table. It can be reduced further by simply having a drink_id column, and moving columns drink and drink_price into a separate table (named drinks below). This would allow n different drinks without changing the database structure. The name and type could have their own tables too for maximum efficiency.
# Weekday perhaps rename to concert_drinks or something
id int auto_increment # primary key
concert_id int # foreign key for concert table
drink_id int # Foreign key for drinks
# Drinks table
id int auto_increment # primary key
drink_type int # foreign key for drink types table
drink_name int# foreign key for drink names table
drink_price float # drink price
# Drink types table
id int auto_increment # primary key
drink_type varchar # description of drink type
# Drink names table
id int auto_increment # primary key
drink_name varchar # drink name
Having drinks, drink types and drink names in separate tables might seem a bit like overkill but this way you can have the same drink have different prices on different days, have different brands of beer etc.
As for adding a drink to a concert, it would be easiest to create an HTML form, add the concert id as a hidden field and allow the user to enter drink type, price etc. Drink type could be a dropdown list populated from the drink types table.
