It is really unfortunate that I've spent this much money and still can't make an iced coffee as good as the Whittier McDonald's

Yes, McDonald's sells McCafé coffee in pre-packaged forms, including K-Cup pods, bags, and cans. These coffees are similar to those served in McDonald's restaurants and are available in a variety of blends, such as Premium Roast and Breakfast Blend. You can also buy McCafe Premium Roast Cold Brew Coffee Packs, which are made with 100% Arabica coffee and can be prepared by steeping them in the refrigerator overnight