In a small bowl add the evaporated milk, sugar, garlic powder, and onion powder. Thoroughly whisk ingredients.
Next, slowly add the vinegar while whisking the bowl until the sauce thickens. Add vinegar until the sauce reaches your desired thickness, but remember, a true Halifax Donair has a slightly runny consistency!
Refrigerate sauce until serving.
Mix the ground beef and lamb in a bowl with all the dry spices listed above until the spices and meat are consistent.
Once the meat and spices are thoroughly mixed, it is very important to knead the meat 5-10 times and then slam the loaf on the counter. Repeat this step 20-30 times. Kneading the meat and slamming is on the counter breaks down the internal proteins of the meat resulting in a paste-like texture providing easy carving prior to serving.
Cook the Donair meat over MEDIUM heat 350F (177C) for 2 hours or until the internal temperature reaches 160F (71.0 C).
Remove from grill and allow the meat to rest for 30 minutes.
Carve the Donair meat into ½ inch slices. Place the desired portion of Donair meat in the pita along with the fresh diced onions and tomatoes. Slather the wrap in sweet sauce and enjoy!