Which response by the coach best increases the client's self-efficacy regarding his sleep goals?

The response that best increases the client's self-efficacy regarding his sleep goals emphasizes his previous successes, reinforcing the belief that he possesses the necessary skills to make positive changes in his current situation. When a coach highlights past achievements, it fosters a sense of confidence and capability in the client. This psychological boost can significantly motivate the client to pursue their goals, as they begin to recognize that they have successfully navigated challenges before and can do so again.

This approach also aligns with the principles of self-efficacy, which suggest that individuals who believe in their ability to succeed are more likely to take action towards their goals. By reminding the client of their ability to improve their sleep habits previously, the coach is instilling a belief that improvement is possible again.

The other options do not effectively enhance the client's confidence in their capability to achieve better sleep. While past disappointments, suggestions of supplements like melatonin, or probing questions about sleep issues may provide some level of support or exploration, they do not directly foster self-efficacy as strongly as affirming the client’s previous successes.