Even McDonald's got this one wrong...not only are cardboard straws awful to use, they don't help the environment.
1) Paper straws are a single-use disposable and still waste the world’s finite resources (water, timber and land for logged trees) as they are re-manufactured constantly to be used for just a few minutes
2) Paper straws cannot be recycled once contaminated with food or drink, so most will end up in the rubbish bin. In landfill, a paper straw will never decompose as there is no oxygen (25% of all waste in landfill is paper!). Thankfully, however, if they are blown into the ocean they will decompose in 6 weeks (although this decomposition will emit CO2).
3) Many major paper straw brands are not FSC certified, meaning they are sourced from non-sustainable forests. FSC certification ensures that wood/paper products come from responsibly managed forests that provide environmental, social and economic benefits to the community local to the forest. Check for the FSC logo on your paper straw supplier's website... if it isn't there then the paper is likely not ethically sourced.
Paper straws quickly go soggy and taste awful, ruining your customer's drink and forcing them to use 2-3 per drink, increasing your use of single-use disposable straws.