Combine the soy sauce, sugar, garlic, lime juice, ginger and red pepper flakes in a wide, shallow baking pan that will hold all of the fish in a single layer.
Stir briefly to dissolve the sugar.
Add the tilapia, and then turn it over so that it's coated all over with the marinade.
Set aside for 20 min or so.
Heat the broiler to high, and move the oven rack to position closest to heat.
Slide the pan into the oven, and broil the fish for 5 minute
Turn the pan around (back to front), and broil for 5 more minute.
If the juices in the pan appear to burn, add a little water to the dry spot.