Okay Guys, brilliant I now have a solution that works even better than I expected.
Thanks to: @JohnS @emre @mxood
This is what I have done in case anyone else ends up in a similar scenario:
I created a product called SET and within the portions I defined all the possible drinks. This includes the inclusive drinks and discounted drinks:
I then created a action called: ADD SET DRINK
A rule called: SET DRINKS RULE:
I used Menu Item Group Code = BREAKFAST and mapped this to all departments.
So whenever I add a Breakfast, the SET product automatically is added to the Order Line and once selected we can then select the required drink from portions list:
This does not only speed up the order taking process but also reduces user errors where sometimes the staff would forget to use set drink and select i.e coffee which would then overcharge the customer.
And most importantly I can finally close the ticket. 