Stars have a lot of mass. The Sun loses almost 5 billion tons of mass every second and has enough fuel to last another 4-5 billion years. Adding a single ton of anything would make no appreciable difference. If you were to drop Jupiter into the Sun, it would have an effect, but Jupiter is only 0.09% the Sun's mass, so the effect would be small.
Depending on how you define a star, you could smush ~13 Jupiters together and make something that is maybe a star. To make a definite star you need ~80 Jupiters. To make it the same size as our Sun you’d need almost 250 Jupiters.