When you need to come up with ideas quickly, it's useful to have a variety of synonyms for "makes off the top of head" in your vocabulary. Some possible alternatives include brainstorming, free associating, freewheeling, improvising, riffing, thinking on your feet, and winging it. Each of these terms conveys a slightly different nuance, so it's worth considering which one fits the situation best. For example, brainstorming might be more appropriate when you're trying to generate a lot of ideas in a short amount of time, while improvising might be better suited to a situation where you need to react quickly to unexpected challenges. Overall, having a range of synonyms for this phrase can help you communicate more effectively and be more productive when you need to come up with creative solutions.