Hi...can i get same effect with coffee to burn fat if i drink hot cocoa from cocoa powder without sugar?

No: Hershey's Unsweetened Cocoa Powder's label says it has 1.5 gram of fat and 3 grams of protein in each 3 tablespoons of powder. That's enough to make a cup of hot cocoa with water, but it will taste "bad" without milk and at least a little sugar. In any case, it has more calories than coffee has. Furthermore, the only way to "burn fat" is by eating fewer calories than a body needs each day.