I have a recipe that's pretty close to some of the better tablita marinades I've tried. I don't know the exact measurements I use (I eyeball it), but here goes...
1 can of Dole pineapple juice (the small ones meant for one person, that come in a 6pk)
3 Tbl fajita seasoning
1.5 Tbl paprika
salt to taste
Put in a bag and mix. Add meat and let sit for however long you want. I usually do overnight. I'll also add onion, garlic or cilantro to the bag if I have some spare.
Note: The fajita seasoning I use is the Fiesta (brand not store). It doesn't contain salt so I have to add that. Some brands are red and have paprika already added, so leave it out if so. Also, some have salt so watch it.
If you try this, let me know.