The Baclaran Market that sprawls around the National Shrine is one of Manila's great bazaars, and at its edges and interior you'll find cheap, fast Filipino food sold at prices that haven't caught up with the rest of the city. Vendors sell pork barbecue skewers, fried fish, rice meals, halo-halo (shaved ice dessert), and kakanin (rice cakes) from open stalls.
This is not a curated food market — it is a working market where the food happens to be very good and very cheap. Go hungry, be prepared for noise and crowds, and bring small bills. The best time is morning to early afternoon; many stalls close or wind down by late afternoon. Wednesday is the most intense day by far due to the novena crowds.