Step 1Combine the grapefruit juice, lime juice and olive oil in an 11x7-inch glass dish. Set aside.
Step 2Cut the root ends off the green onions and trim most of the green tops, leaving about 1 1/2 inches of the white part with some green at the top.
Step 3Thread the shrimp and the green onions on 2 (10-inch) skewers in this order: 1 shrimp, 1 green onion, 2 shrimp, 1 green onion, 2 shrimp, 1 green onion, 1 shrimp. When skewering the shrimp, make sure the skewer pierces the shrimp twice, once in the large end and once in the small end. Season the skewers with salt and pepper and place them in the marinade for 10 to 15 minutes, turning them over every few minutes.
Step 4Meanwhile heat the grill or a well-seasoned indoor grill pan over medium-high heat. Make the glaze by combining the garlic sauce and honey in a small bowl. Mix well and have a brush ready for grilling.
Step 5Grill the skewers until the shrimp are pink and brown around the edges and no longer translucent, 1 to 2 minutes a side. Brush with the glaze while grilling. Sprinkle with cilantro and serve.