If your rabbit is just having a pee accident, often they may give you a nip or dig at your clothes to get your attention that they want down, which could be if they want to pee. If you are actually getting sprayed and not just a puddle from an accident, that is usually a territorial, irritation, or hormonal thing. Which if hormonal would require a spay/neuter. If your bun is already fixed, with territorial, maybe some positive reinforcement training may help. If it's because your bun is irritated, don't do whatever is irritating your bun.
Then there are the possibilities of it being a health issue if your bun seems to be loosing bladder control, and/or is dribbling urine and getting a wet bum. Which would mean an appt. with a knowledgeable rabbit vet. A bun could possibly also let loose a puddle if completely relaxed, though not common.
If they're about to spray they usually sniff something intently then raise their tail before they spray. If they just need to pee they give more warning. They usually will nip or dig to ask to be let back. My rabbits usually tense up, spread their feet a bit apart and take a couple steps back before they go as well.