Even though there is no account whether Jesus did drink during his 40 day fasting, there were already other accounts where fasting was devoid of not just food, but water as well. Such as Moses' 40 days in Deuteronomy 9:9, Acts 9:9 of Paul's 3 day fasting of conversion, and Esther's 3 days in Esther 4:16.
Of course, the purpose of fasting is not to show off one's endurance, but one's true desire to rely on God.