Get a gallon ziplock bag, your pork tenderloin, marinade, cutting board, and a knife.
This is the brand of tenderloin I get. It's from King Soopers. I think it's "sooper" good (sorry, couldn't help it) and really affordable. I get 1 of them and it will feed about 4 people, or Matt and I will have dinner plus leftovers.
I cut my tenderloin into slices after cutting all the fat off. Most people don't. Most people cook it as is then cut it up at dinner. But most people get to sit down and have nice family dinners. I NEVER eat fresh food! I cook food that pretty much goes directly into stacked tupperware because Matt and I never see each other for meals outside of the weekend. Maybe when we "grow up" that will change. The habit stuck and even when I'm cooking it for guests I pre-cut them into slices like this. Put all the slices in the bag and dump your whole bottle of marinade in it.
You're going to have this gross, runny, bag of blackish liquidy stuff in your frig. I like to leave mine at least a day to soak in the marinade (even if the bottle says "30 minute marinade"). Let yours soak as long as you like because cooking it will also soak in the flavor and you already made them small pieces. Just please cook it at the longest on the third day, cause this is a bag of raw meat and that's gross.
I dump the whole bag in a glass baking dish and cook in the oven at 350 for starting at 30 minutes and increasing as I need. Every cooking time is a little different. Good news is it's hard to burn because it's marinating the whole time so it will just keep getting yummier for a while. I normally leave mine closer to an hour until the sauce on the edges of the pan starts to burn a bit but nothing else is burning. That's a good stopping point. 45 minutes to an hour.
When it's done you have this really soft, tender, very flavorful, tenderloin. I love it so much. I love serving it with rice, sometimes with pineapple to match the teriyaki and make it a bit Hawaiian. Yesterday I had it with just a side of veggies. It's a large pan of meat; you can do whatever you want with it! It tastes fantastic!
Hint: I have also frozen it in the marinade raw and frozen to make the serving size for just 2 people and stock up my freezer. This is a staple at our place!