For an alternative to mayonnaise, consider alternatives such as yogurt, sour cream, or avocado. Yogurt can provide a delicious tanginess and creaminess to your crab cakes; just be sure to choose a plain Greek-style yogurt since flavored varieties can be too sweet. Sour cream also works well as a mayo substitute in crab cakes. It will give the dish a slight acidity that pairs nicely with the other ingredients. Avocado is another great option for those looking for vegan options--it adds a creamy texture and flavor that pairs nicely with the crab without overpowering it. Plus, avocados are high in fiber and healthy fats, making them a healthier choice than mayonnaise!