Could you help me out just a little?
Can I have just a tiny taste?
この服、ちょこっと大きいかも。
These clothes might be a little big.
I only ate a little bit of the snack.
Just wait a moment, okay?
たっぷり means 'plenty, generously' while ちょこっと means just a tiny bit, so they describe opposite amounts.
ちょこちょこ (repeatedly, in little bits over time or with quick small movements) sounds similar to ちょこっと but describes frequency or motion, not a single small amount.
Colloquial variant of ちょっと, likely formed by reduplication or playful sound change. The exact derivation is uncertain.