4 drinks and a cup of skimmed milk is kind of like sole source plus now. sole source is 3 or 4 cambridge meals, depending on your height (for men it's always 4 cambridge meals, and for women over 5 ft 8 it's also 4 meals).
sole source plus is either 4 cambridge meals and skimmed milk, or 3 cambridge meals and a small meal, such as lettuce with chicken breast.
then u have the 810kcal option, which is also 3 meals and a larger meal, but pretty much same ingredients as in sole source plus.
with the 1000, 1200 and 1500kcal plans is more complicated, u've got more options, but don't have them all in my head