ちゅるちゅる

Meanings

adverb, adverb taking the 'to' particle, noun or participle which takes 'suru'

onomatopoeic or mimetic word

Mimetic adverb describing the sound or manner of slurping noodles or sniffling a runny nose. Often used with と or as a する verb.

つるつる
つるつる also means smooth/slippery but is more common and neutral; ちゅるちゅる adds a nuance of slurping or a childlike feel.
ずるずる
ずるずる implies dragging or slurping heavily, often with a negative or messy connotation, while ちゅるちゅる is lighter and more playful.

Onomatopoeic word mimicking the sound of slurping or a smooth, slippery surface. The exact origin is uncertain.