Is there a good way to get your teenager to avoid drinking soda all of the time?

Yes. Don't buy soda! and further limit the money your child gets if they don't stop buying the soda.
Don't subsidize/use. Parents of teens have more influence than they think & some obvious tools that are overlooked.To decrease soda use, don't pay for any more and commit to there being none in the house. If you think a soda sunday is cool, make it happen, but don't think a teen will comply with half hearted measures. If they go to the "cool parents " house to drink sodas, let them, & let them know you love them anyway.