The chances of becoming obese are extremely high if you go to Burger King and drink sugar-filled soda. The cup's ownership doesn't matter here.
Remember how at school, after laborious physical education lessons, everyone drank saving water from one bottle. I won't guess, but I think that there are many people among us who have done this.
And in extreme cases, you can gently rinse the drinking part of the glass under the apparatus (some soda).