Option one is to have Contrary, but no Pokemon that gets Contrary also gets Overheat. You have to Skill swap the ability onto the Pokemon with Overheat, for example, Spinda. The second option is to use Firium Z. This negates the special attack drop and boosts Overheat's power. The third option is to use a White Herb, but that's a bad option instead of Leftovers, Life Orb, etc.