Toss cucumbers with vinegar in small bowl. Reserve for later use, stirring occasionally.
Cook rice in large nonstick skillet as directed on package, omitting salt. Spoon into 4 bowls; cover to keep warm.
Add meat to skillet; cook until evenly browned, stirring frequently. Meanwhile, mix next 4 ingredients until blended.
Add garlic sauce mixture to meat; mix well. Spoon over rice.
Top with cucumbers, onions and sesame seed.