It's very easy to get a lot of unwanted noise when bending strings on the guitar. You must be able to mute out adjacent strings to the one you're bending.
Some things that can help is to always use your picking hand to mute out all strings lower than the one you're bending. That means if you're bending the G string, your hand should be aiming to mute the E, A, and D strings.
If you're bending the high E string then you'll be trying to mute out the E, A, D, G, and B strings.
Having at least one finger on the fret hand muting the adjacent strings helps too. Let's take your index finger for example, and you're bending the B string. Your index finger needs to be barely touching the G string AND the high E string.
These ideas will make a lot more sense after you watch this video:
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John Taylor - guitar and bass instructor for Mile High Shred.