Stem the chile. Split the chile in half, remove and discard the seeds and membrane. Finely chop the chile. Combine the chopped chile, garlic and sugar in a mortar. Pound the mixture into a paste. Remove the zest and pith from the lime, and discard. Add the lime to the chile mixture. Mash well. Add the fish sauce and the water. Mix well. Serve as a seasoning agent instead of salt and pepper.