Take a hair product that is glossy or something that will make the floor slippery like gel or oil. Take the hair product and spray it on the floor where your brothers door is or in front of the bed if he is sleeping, then when he gets up or comes out he will slip on the floor. Don't do it if he has a back problem or will break a bone.
Put salt on his toothbrush. It is harmless but get ready for an insanely funny reaction. Plus check the next one below:
We take drink bottles to school, once I opened my brother's drink bottle and squeezed some toothpaste into the spout, not a lot, just a little, it did the trick and I mad sure I had a good view of his experience with my friends during break time. We killed ourselves laughing.
When we got home he played a ton of pranks and game tricks on me, so I did regret it in the end.