Ponzu is a Japanese citrus-based sauce commonly used in cooking and as a condiment. However, if you're looking for a substitute for ponzu or just want to try something new, there are several synonyms to consider. Yuzu, a Japanese citrus fruit, is the primary ingredient in ponzu, so you can use yuzu juice as a replacement. Another option is using a combination of soy sauce and lemon or lime juice, which will give you a similar tangy flavor. Tamari sauce, which is made from fermented soybeans, is another great substitute. Finally, you can try making your own ponzu by combining lemon or lime juice with rice vinegar, soy sauce, and sweet mirin.