In a small bowl, whisk together flour, baking powder, baking soda and salt.
In a large mixing bowl with paddle attachment (or using a hand-held electric mixer), beat the eggs and sweetened condensed milk until combined. Add flour mixture and continue mixing until just combined.
Form the dough into big log and wrap it in a plastic wrap. Refrigerate for about 30 minutes.
Heat the oil (about 2-3 inches deep) to 315°F (115°C).
While the oil is heating up, bring out the dough onto a counter. Cut the dough into 4 thinner logs lengthwise. Then cut into small pieces and roll into ½-inch balls.
Deep-fry dozen or so balls at a time for about 3 minutes, or until golden brown.
Using a slotted spoon, transfer the cooked donut holes onto a baking sheet lined with paper towel and wire rack. If desired, roll the cooked donuts in sugar while hot.
Once cooled completely, store in airtight container at room temperature for up to 3 days.
For step-by-step photos and additional notes, read the post above.