Can cyclic hydrocarbons have an sp hybridized carbon?
No
No, a cyclic hydrocarbon cannot have an sp hybridized carbon.
Take a look at this molecule for example. Let's think about the carbons in this case. These carbons need to have some freedom so that they can form a ring right?
But in the case of sp carbons, they are rigid and linear. If they were involved in a ring, the angle strain would be too high and the molecule would become too unstable. This is why we can't have a triple bond in a ring structure.