I love trying new things and I found this recipe for Cola Marinade at Foodgeeks.com. I tweaked it a bit and tossed my roast in the zip loc bag.
1/2 cup lemon juice
1/2 cup vegetable oil
1/2 cup balsamic vinegar
1 teaspoon fresh ground pepper
1 teaspoon fresh ground salt
3 tablespoons minced garlic
1 can cola
1/2 cup Worcestershire sauce
Put your large zip loc bag inside a measuring cup, folding the edges over the cup. Add all the ingredients into the bag.
Remove the bag from the measuring cup careful not to spill. Add a 4-5 pound sirloin beef roast.
Seal the bag, put the bag in a bowl and put it in the refrigerator for up to 24 hours.
Let the roast sit at room temperature 1 hour before putting on the grill.
Tie the roast onto your rotisserie. Preheat the grill to 400 and insert the rotisserie onto the grill. Add a drip pan underneath with 1 cup of water, check to make sure the water doesn't run dry, or you will have very scorched drippings.
Grill with the lid closed for 1 hour, check the temperature. You will aim to have the internal temp at 135 - 140. We let ours cook to 154 and it was completely done, no pink left. Next time we will take it off the grill at 140. Remove from the heat and wrap in foil for 15 minutes.
During the resting time we grilled our chopped up veggies in a grill basket. I simply toss the veggies with veggie seasoning and olive oil and stir them once in a while. They only need 10 - 15 minutes on the grill.