Their needs to be a penalty. Another 17 cents on my coffee just dont mean anything when I buy a $4,50 coffee at Starbucks.... (I usually dont buy at Starbucks, but the point stands)
A penalty, or a reward for reusing the container. If your coffee became $3 and you buy one or more a day, that's a reasonable saving over a year for the customers. Pin that with something that makes a public statement that you care about the environment and perhaps there's something here.
