You are not supposed to make anything with them. In the green book (my journey) given to me when I joined 5 weeks on page 20 it says:
Ready steady dont cook
Whilst our porridge and chilli are specially formulated to withstand cooking according to the insstructions, don't cook any other foodpacks - which means no baking, making muffins, grilling, microwaving, boiling, barbecuing, toasting flambeing, deep fat frying or making crisps. Heating them could compromise some of the nutrients they contain. which means reducing the quality of your daily nutrients. In the longer term, this could be detrimental to your health. So even if you are given a "black market" recipe sheet, just say no.
However it does seem you can heat the shakes to make a hot drink.
However I shouldn't think the odd occasion would make much difference, not just every day.