Disney Baymax Tumbler with Straw

I bought this a few months ago at a Disney store in my local mall. I thought it was really cute and I loved it for the first few uses. But soon I noticed random brown stains and mold like shapes in my straw and lid. After putting the cup away after being washed, the cup also collected old water dripping from the lid. I have used a straw cleaner, scrubbed the lid and base and I still can’t seem to get the mold to stop. Not worth the hassle or money.