From the Super Mario Wiki
Fire watermelons, also referred to as red watermelons, are hot, fiery red watermelons in Super Mario World 2: Yoshi's Island, its remake Yoshi's Island: Super Mario Advance 3 and its sequel Yoshi's New Island. If Yoshi eats this fruit, it will allow him to shoot fire thrice in the original game and five times in Yoshi's New Island, which can be used to defeat enemies, melt Ice Blocks, and deal more damage than a regular green watermelon in the Mini Battle Game Watermelon Seed Spitting Contest.
The Super Red Watermelon Special Item is available in Super Mario World 2: Yoshi's Island and Yoshi's Island: Super Mario Advance 3, and the All-you-can-eat fire watermelon! Power Badge is available in Yoshi's Woolly World. Using them automatically places a fire watermelon in Yoshi's mouth, allowing him to have its ability at nearly any point. In Yoshi's Island, using a Super Red Watermelon allows Yoshi to spit fire nine times instead of the usual three.
Yoshi's Island: Super Mario Advance 3
Names in other languages
Super Red Watermelon