All it takes is just a pull of a string.

Source: Manila Bulletin (https://mb.com.ph/2020/11/23/want-hot-and-delicious-meals-anytime-anywhere-try-these-innovative-self-heating-food-boxes/?utm_source=rss&utm_medium=rss&utm_campaign=want-hot-and-delicious-meals-anytime-anywhere-try-these-innovative-self-heating-food-boxes)