I second Wascally Wabbits, cat laxative for a bun with a blockage is not sth I’ve heard of either. What’s the name of the laxative?
Did the vet do an X-ray of your bun’s tum? Did your bun get any sub-q fluids? Hydration is key when you’re dealing with a blockage and often, fluids by mouth is not enough.
Pineapple won’t really do any good except provide the bun with some sugar and stomach content, which he might need at this point.
Will he move around if you put him on the floor? Exercise is good because it helps the intestines move. Not vigorous exercise of course, just a bit of moving around.
A bunny with a GI problem often gets cold (hypothermic). It’s very important to keep the bun warm. It’s good if you can sit him in your lap and put a light blankie on him, that way your body warmth will help him get to the right temp with no risk of overheating. You can try to elevate his butt slightly so any trapped gas can escape more easily -gas is painful for buns and often follows on other GI problems.