Probably honeydew - the 'spit' secreted by aphids/greenfly etc that are feeding on the sap of your vine. Wash off with a soap solution (use 100% soap flakes not detergent) and make sure you get the underside of the leaves. You may need repeat applications a couple of weeks apart. If that doesn't clear it, you'll have to resort to a branded insecticide but please be careful and don't choose one containing neonicotinoids, as these are cited in the demise of honey bees.

There is no pic but my guess is the same as Urbanite!

Be useful to know what the 'vine' is - if its a Hoya and its in flower, the stickiness could just be the nectar dripping from the flowers.