Be careful! I believe that spray nozzles are fluidic oscillators precision molded of relatively soft plastic.
Unless one has carelessly introduced foreign trash, the likely substance disturbing the flow pattern is organic slime. If one still has good flow through the nozzles then I would flush and drain the reservoir (separately if possible) and then put in a liter of cheap alcohol - isopropanol, methanol or ethanol - to denature the organics and spray spray spray.
When I learned of BMW's tendency to foul the reservoir, pumps and nozzles, I quit using patent solutions and use distilled water and vodka. As winter approaches I'll refill only with vodka.
be aware that the washer jets on the F10 (at least, on my F10 535i 2010) are NOT adjusted by using a needle or something like that. They are fixed to a larger piece of plastic, and on the back lower side there is a screw that you can rotate to aim the jets to the windshield. Don't use too much presure moving the screw, because you can broke it (it's plastic!).
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