Throw the peppers (Jalapeno and Serrano), salt, sugar and garlic into a blender; add water. Blend the ingredients until smooth.
Transfer the blended puree into a glass jar or a container. Cover the container with plastic wrap and place it in a cool and dry place for three to five days. Stir the blend and scrap down the sides of the container every day. Rewrap after every stirring session, and return the jar to a cool and dry place. Wait until the mixture becomes bubbly.
Pour the blend back into your blender. Add the white vinegar and blend the mixture until smooth. Strain the mixture with a strainer with a fine mesh. Discard the seeds, skin and pulp left after straining.
Transfer the smooth sauce into another saucepan. Boil it over medium heat, and remember to stir the mixture regularly until it reaches the desired thickness.
Let the boiling sauce cool slowly to room temperature. It will thicken as it cools. After it cools to the desired temperature, transfer it into a bottle or a jar, seal it tightly, and then place it in a refrigerator.
