utilizing Facebook adds, youtube adds and Instagram adds is the best because it reaches a wider and more precise target, especially for those who are food enthusiasts.
I do not think this forum is best for promoting the food app. You need to think about other marketing strategies as here we only discuss about cryptocurrencies. If your app is based on Blockchain technology with the use of tokenomics then you can create an ANN here.
These forums are good enough for marketing but don't reach very broadly...