1. How many spoonfuls of sugar woud you like?

2. How many spoons of sugar would you like?

3. Add two spoonfuls of sugar in the coffee.

4. Add two spoons of sugar in the coffee.
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Do we have to use 'spoonfuls' or 'spoons'? Are both OK? Then, which one is commonly used?

spoonfuls is more common in my experience. Two spoonfuls is a lot of sugar.