“I don’t care what you do” is one of those phrases that can be misinterpreted because it can have several different connotations. It can be understood as “I don’t have a particular preference, all options are OK with me.” It can also mean “You and this whole issue aren’t important to me.” Or so many other things – depending on the context.

Use the phrase with thought. Or change it up to say what you really mean.
– “I am not attached to any particular outcome.”
– “I don’t have a preference. All options are reasonable.”
– “How about we change the topic to something we both can participate in?”
– “I don’t have an objection.” “I don’t mind.”
– “I need to think about it a bit more.”
– “This is a bad time.”
– “I sense that you feel strongly about this, but I’m not sure I understand why. Please help me understand.”
– “I do not care much about this.”
– “I could go either way. Which do you prefer?”
– “This doesn’t bother me either way, so let’s go with what you would like.”
– “I’m indifferent about this, so go ahead and choose what you would prefer.”
– “I understand that’s important to you but it’s not important to me.”
– “I’m not really into that.”