how do you make ice coffee like McDonald’s does?

i bought the syrup at sam’s club it’s called da vincis original hazelnut syrup i made some put it does not taste anything like McDonald’s ice coffee can any one tell me how to make it. i got coffee from this morning and 2% milk with regular sugar but it taste ugly. does any one that work at McDonald’s tell me how you guys make it and if the syrup i have is the same one that you guys use please let me know thank you o and if the ingredients i am using are they the right ones to use or should i use something els