4 oz of dr. mcgillicuddy's vanilla schnapps (or Vanilla Schnapps)
20 oz of bottle dr. pepper soda (or Grapefruit Soda)
Drink or pour out a couple oz of the Dr. Pepper (down to bottom of the buldge of a 20-oz bottle) then top off with Dr. McG's. If your soda isn't cold, the drink can be poured over ice, but it's better cold and straight up.