You mean like baking cookies and cakes? Some good subs for eggs in baked goods are Flax "eggs" (1/4 cup water heated with 2 tbs flax meal added, stirring every few minutes = 1 egg), apple sauce or oil. For any milk you would just use plant milks, like soy or almond. If your friend is in the UK, you don't have to worry about the sugar, but in the US, it is often filtered with bone char. So no need to worry on that one. Cocoa baking powders are vegan, but be careful with dark-chocolate chips, many of them now have whey powder in them.
I guess I need more info on what sorts of things you will be baking...