Don’t Let Your Cat Eat Dog Biscuits
Dog biscuits should not be considered a good substitute for cat treats. Dogs and cats have different nutritional needs and dog biscuits have most likely been formulated to meet whatever dietary needs an average dog requires.
What may be toxic for cats might not be toxic for dogs. There is also a risk of letting your cat eat dog biscuits with ingredients that are exclusively harmful to felines.
Generally speaking, a cat is unlikely to get sick from eating dog biscuits (unless it contains toxic ingredients) but it may introduce long-term health problems if they are given these biscuits consistently. You shouldn’t have to worry if your cat accidentally ate one or two dog biscuits. Just make sure it doesn’t become a regular habit.