As other answers have noted, blood contains fairly little glucose (blood sugar), so that makes for weak drinks unless external sugar is added, or the glucose is somehow extracted and distilled separately from the rest of the blood.
If you don't mind taking a dark turn, you could spin this into a world where human diabetics are farmed for high glucose blood.
Diabetics can have much higher glucose levels than humans, and while that is a big problem for anyone suffering from diabetes, it could be an opportunity for vampire wine-makers.
Wile normal blood sugar level would usually be below 7.8 mmol/L 2 hours after a large meal, diabetics can go higher - much higher. In 2001, a diabetic was admitted to a hospital with a glucose level of 147.6 mmol/L (source: Guinness World Records - highest blood sugar level)
So you could have an economy where "harvesters" track down and capture "Gilberts" (makers of vampire wine call diabetics Gilberts, after the movie Gilbert Grape), and them bring them to "wineries" where they are force fed candy (and probably also alcohol) until glucose levels spike to a lethal level, where upon they are murdered by having the sugar-rich blood drained to a fermentation tank.
Even if the blood loss did not kill the victim, the high glucose level would, from organ failure. Some blood farmers probably prefer to keep their grapes "on the vine", meaning that they are kept alive for longer periods of time, with blood drained over a number of sessions - perhaps they are even treated with blood transfusions from non-diabetics (whose blood is less valuable to the vine maker).
Keeping Gilberts "on the vine" is also referred to as "milking"; most blood wine connoisseurs prefers wine from sources that have been "squashed" (all blood drained in a single session), these wines are seen as more pure - where as milking Gilberts is seen as cheating/low quality.