If I didn't have a diabetes diagnosis I'd say my favourite cold drink is a granizado de limon ( a sort of proper lemonade slush puppy) particularly suitable for drinking on the way from one cafe to another on a hot and sunny day in Seville. Or a Lime Daiquiri on the beach at Varadero. Or a Bombay Sapphire with elderflower cordial, ice and soda water, which can be satisfactorily drunk almost everywhere.
With my diagnosis, and not being a fan of sweeteners, I tend to cold sparkling water with lots of citrusy slices in for a bit of flavour.