Hello, my name is***** and I have over 20 years of experience as a veterinarian. I understand that you are a bit concerned about Sonic not drinking much yet seeming to produce a significant quantity of urine.
"Raw" diets tend to be significantly higher in moisture content than the typical dry dog food. Fresh meats, vegetables and fruits are high in water content. Thus he may not need to drink much to have more than enough fluid intake. Pushing him to drink more fluids will only result in more urine if he is already well hydrated.
However if he does seem to produce more urine than a normal dog would, even given his high moisture content diet, it would be a good idea to check a urinalysis to look for any underlying issues that could indicate why he seems to produce more urine.
I would look at protein content, increased levels of glucose or bilirubin in his urine, increased numbers of red or white blood cells, bacteria levels, as well as concentration level of his urine on a urinalysis. That would be a quick, easy, and relatively inexpensive way to look for health problems.
Please let me know if you have any further questions.