I'm guessing this is for the vitamin C? I wouldn't have thought it would be a great idea - it's full of sugar and doesn't actually contain much vitamin C anyway.
Someone I know used to put dissolvable vitamin C tablets in her pigs' drinking water and said they lived for ages and were never ill. I don't know whether this is safe or not. We just used to give ours plenty of fresh greens and carrots and they seemed to be alright!
I've never given Ribena to the hogs but I would if I have to persuade them to have medicine and wanted to mask the taste. It does contain a load of sugar though (and I don't give my DC the low sugar one because I worry about artificial sweeteners).
My (human) son helped himself to a glass of Ribena when he was little - but didn't dilute it. He had the worst dose of the runs after
So I'd be wary of giving too much to hogs (especially as my GP2 has an unreliable backside with a regular guinea diet)