How to make sweet-tasting noodles?
Butter and milk will add fat and water which will definitely change the consistency of the dough. You will have to adjust the ratios if you add them (surely more flour if you add milk).

If you want sweet noodles my best bet would be to add sugar, although I wouldn't do sweet egg noodles... maybe sweet rice noodles?

Why don't you just do plain noodles and then make a sweet condiment instead?