Slice Serrano chilies at a diagonal about 3/16th (5mm) thick. Place in a colander and give it a good shake to remove as much of the seeds as possible. Peel garlic. Discard blemished cloves. Wash and pat dry with paper towels. Leave bird’s eye chilies whole.
Sterilize 2 jars sufficient to hold all the chilies and garlic. I like to throw in the lids for just 3 to 5 minutes towards the end.
Place sliced Serrano chilies and peeled garlic in one hot jar and bird’s eye chilies in another jar.
Combine vinegar, sugar, and salt in a small saucepan. Place on the stove and bring it to a boil. Stir to dissolve sugar and salt.
Pour hot liquid into jars to cover chilies and garlic. Place lids on jars and allow them to cool on the counter. When cooled, transfer to the refrigerator.
Leave sliced Serrano chilies and garlic to pickle for 3 days and bird’s eye chilies for at least a week before serving.
Consume pickled Serranos and garlic within a month and pickled bird’s eye chilies within 2 months.