Place chicken drumsticks in a bowl and add vinegar, pepper, adobo and oregano. (add Sazon if using it) Mix everything well and let marinate for 15-20 minutes.
Cut all of your vegetables while the chicken marinades.
Set your Instant Pot to sauté mode and heat the olive oil.
Add the chicken pieces to the pot and brown them on all sides, about 3-4 minutes per side.
Once the chicken is browned remove it from the Instant Pot.
Sautee onions and add sofrito to deglaze the pot.
Add the tomato sauce and water and mix well.
Add remaining vegetables and chicken to the pot
Close the lid of the Instant Pot and set the vent to the sealing position. Cook on high pressure for 8 minutes. (cook for 10 for softer meat)
Once the cooking time is complete, manually release remaining pressure.
Carefully open the lid of the Instant Pot and give the Pollo Guisado a good stir. Taste and adjust seasoning if necessary.
Serve the Pollo Guisado hot, garnished with olives, capers, or fresh cilantro if desired. Enjoy with white or yellow rice, and your favorite side dishes.