How about a separate oscillator into an MDAC? Only need to update it once in a while. By "sine wave" I presume there are no phase or frequency changes; or really amplitude either, as a sine wave is eternal. But "sine wave" is typically used loosely, so I'm making light of these here...
...Which can be injection locked, or digitally tuned; of course the hardware-complexity tradeoff quickly gets out of hand, but there may be a middle ground where it's suitable.
Also, distortion, spurs, etc.? SINAD? Not crazy I guess if 12 bits is adequate, but depends on how much overhead you need for the sample rate.
(If distortion doesn't need to be impressive, it could even be a well-filtered timer output (square wave) into an MDAC, in which case phase/frequency is directly controllable again.)
Tim