Can I eat ice cream and stay in ketosis?

The answer is yes/no. Regular ice cream contains a lot of sugar and carbs which can spike your insulin levels, and it will kick you out of Ketosis. However, there are a lot of Keto version ice creams on the market. You will need to look for ice creams where carb levels are low and in which sugar substitutes are used like erythritol, stevia, etc.