Mum, can I stay inside and watch cartoons?
__________. I need you to help me in the garden.
In the above blank, the most suitable phrase would be No way. That would indicate the mother's reluctance on her child watching cartoons, instead of helping her with her chores.
no way - under no circumstances; no or not in any way; used to tell someone that something is impossible Source
"Can I go with you guys?" "No way – this is just for big kids."
forget it - used to tell someone that what they want is impossible Source
"I'd like to take next week off." "Forget it, we're way too busy."
Now, according to the meaning and the examples, both the terms are very similar to each other. In many cases, they can be used interchangeably as well.