Sorry don't know if they are edible but would imagine so once you have added something to make them more palatable.
I guess with the flavouring it really depends on what 'agrees' with you. First thought would be the milk shake powders (like Nesquik) that is usually added to milk. If you are a coffee or chocolate drinker maybe you could dissolve some in a small amount of boiling water then add it to chilled peptamen. Flavoured icecream mixed in might be good(or sorbet). If you aren't too bad with eating then how about mixing it with angel delight? Or adding fruit that has been polverised in a blender?
If the peptamen is unflavoured could you possibly use it as a 'milk' substitute in an 'ordinary' recipe? Just a thought.
If all fails maybe a thread about
101 alternative uses for it may be interesting