How do I get my dog to take pills when she is always uncooperative?

My dog is almost 15 years old and was recently prescribed some pills. She refuses to eat them with treats (she will literally bite them in half, drop them on the floor, then inspect the treat before eating it, same with things like cheese). She's so suspicious of everything. She also refuses to eat peanut better recently so we can't use that. Even when resorting to using one of those pill syringes, we can't even get her to keep her mouth open. I know the technique of grabbing right behind the canines, but every video I watch has a dog that just sits there, no wiggling, no squirming, no pulling away. It's stressing me out that I can't get her to take the pills.

Anyway, if you have any tips or tricks to use, I'd love to hear them.