Plaintext question. Obviously, rampant googling might occur, but then again we trust you to not do it, so please don’t :P

“Formal” syntax of what?
Accept-Additions = “Accept-Additions” “:”
#( addition-range [ accept-params ] )

    addition-type   = ( "*"
                      | milk-type
                      | syrup-type
                      | sweetener-type
                      | spice-type
                      | alcohol-type
                      ) *( ";" parameter )
    milk-type       = ( "Cream" | "Half-and-half" | "Whole-milk"
                      | "Part-Skim" | "Skim" | "Non-Dairy" )
    syrup-type      = ( "Vanilla" | "Almond" | "Raspberry"
                      | "Chocolate" )
    alcohol-type    = ( "Whisky" | "Rum" | "Kahlua" | "Aquavit" )

Cracked by: Sumanth Patlolla, Bharath, Rogi, rickde, Manish Achuth, Ananth, shrik, Vishwas B Sharma, rohanquizzer, KK, Shwetha Maiya, siddhanthrao and jowens