Some people add cinnamon to the shakes. Then you have the mint choc option, you can add a spoonful of coffee to vanilla or chocolate shakes to make a mocha or latte respectively and can have them either hot or cold. You can also make the chocolate or vanilla sachets into a mousse - instructions for this are on the LT bag.
As for the soup I know of people adding chilli flakes, paprika, cumin, assorted ground pepper, garlic and a number of other things. Salt is a definite no no, however.
And drinks - black tea like peppermint, green, redbush, nettle (any pure leaf tea, no fruits/berries/flowers ie Lady Grey, camomile or fruit infusions and NOTHING containing lemon or any other form of citric acid), black coffee, and water.
Sweeteners are fine as long as they are in tablet form and are not the spoonable kind that looks like sugar.
Hope this was useful.