I have an unopened packet of baseball cards, still in the cellophane wrapper. They are made by Donruss in 1992 and evidently are a Coca Cola series of some sort. The top card is Nolan Ryan, Astros, 1986. The bottom card is Brian Jay Downing, Rangers, 1991. Is there any way of knowing what the other cards might be without opening the pack or how much the unopened pack might be worth?

I'm afraid they aren't worth much of anything, sorry.
There's a similar one right now on eBay, '1992 Donruss Baseball Card Coca Cola Unopened Pack' for 3.99.
I don't think that your 1986 Nolan Ryan makes any difference, because none are original cards.