I won't give my opinion on the Carnation because I'm not sure, but I want to suggest something to get him drinking water again on his own.
Last year my girl Mustard got sick and dehydrated very quickly. She wasn't drinking on her own so I would syringe her some water, and HedgeMom (RIP) suggested offering her water sweetened with a little bit of honey. It worked like a charm, she slowly started to show some interest and after a couple of days was drinking good amounts of sweetened water. I don't know if it will work with Beck, but it might be worth a try.