Don’t get me wrong, if you have a good jam or preserves it’s totally fine on a sandwich, and I wouldn’t turn my nose up at it. However, peanut butter doesn’t really need the help, and the extra sweetness from jelly is totally unnecessary. Toasted bread and peanut butter is all you need for a quality simple sandwich.
I prefer it with cucumber myself. Ads a nice fresh crispness to it.
Pickles are good too. I haven’t done it with cucumbers in a long time I might make that tomorrow