The cup even after repeated rinsing stinks

I could not even try if the Cup works for my 8 months old son. The 'slope' of the cup is not its form but its chemical smell, which disappeared in the dishwasher either after washing by hand even after rinsing. The water in the cup takes on a strange, unpleasant aftertaste. Try it yourself before you add the water to the little ones. Now I have the cup 'inserted' in a bowl with detergent for several hours. Now he does not smell.