You can buy whey powder that contains no sugar, no flavours etc so all you need to do is mix it with milk.  I got a recipe book from Marks Daily Apple website which has heaps of different recipes for replacement shakes (my fav was banana bread, which was water, protein powder, banana, cocoa and ice.... so yummy and refreshing as breaky on the go).  Also Aussie Bodies Perfect Protein Powder is perfectly safe, contains stevia and xylitol (on David's your call list), they have plain (no added sweeteners), vanilla and chocolate flavours.  You can get Aussie Bodies from your chemist (only the protein powder is acceptable, their other products contain nasty sweeteners).