If you mean in the context of that day, it would be more appropriate to say "I took two baths today"

Both are strange things to say but the first is correct English and the second is not. I can imagine someone saying, "I have taken two baths today" but to tell someone you have taken two baths, without reference to time, sounds like you have only taken two baths in your life time. This might not be understood correctly unless you don't own a bath tub.