DL can be picky about quotation marks.
"" and ““ are OK but “” are not - they are all quotation marks generated by different keys from different keyboard layouts. I think general UK layout uses the same key for opening and closing quotation marks but some layouts have separate opening and closing quotation marks which might look similar in certain fonts but which have different keycodes.
You never noticed it like that. After a lot of discussion I have discovered where the problem is. On bottles and cans they always substitute the hyphen with some graphic or other (which changes over time). So you don't realise it is a hyphen. Look carefully at a bottle or see the images in this link.
But I challenge you to find it with nothing between the two words.
It has been drunk by Gaelic speakers since before most people could read Gaelic, so its spelling does not affect its pronunciation. It is just pronounced as it is in English. It is not normal to change the pronunciation of English words unless it is something that is difficult for a Gael to say, such as modern which becomes modren.
OK, if the manufacturer's own web-site doesn't convince people, here are links to the UK Government Trade Mark site:
sousquark has posted a link to Barr's website each time someone says it is two words. Barr clearly shows it is one word with a hyphen. So it is one word. Their brand name is usually shown on products and advertising with one of various graphics between the two parts of the word that are clearly meant to represent the hyphen even if it is not obvious.