Here's an idea for today. Pretend the plumber is coming to fix your kitchen sink. Pull out everything in preparation, as though he's going to have to stick his head and shoulders in there. Look through all you pulled out. Does it really need to go back in? Sort through it. Wash the cupboard walls if needed. I have a handled bathroom tote I keep under the sink that stores all my cleaning supplies in one spot. I would recommend some container so that when it's filled, you know it's time to stop buying additional cleaning supplies.
Once everything necessary goes back under the sink, work at keeping it neat so that you can easily find what you want to use. A future plumber will thank you.