Think of something in the room and tell your child they can ask questions to work it out — but you will only answer yes or no.
When they guess wildly instead of asking, gently steer them back: 'that is a guess. What could you ask me?'
Swap roles for the second round. Asking is harder than answering, and both directions are worth practising.
A yes-or-no constraint forces a child to convert a vague hunch into a precise question, which is a real linguistic and logical operation. Narrowing a field of possibilities by asking is the root of both inquiry and deduction.