some reflux bubs have a hard time with cereal because it can be harder to digest. You could try something like sweet potatoes maybe. Honestly, rice cereal for babies is pretty flavorless, I can't really blame him. Also, when are you offering it? It's best to do solids 1 hr after milk feeds. And at 5 months, there's no big rush to start solids. We waited til 6 mos. Until he's a year, milk is still his primary source of nutrition, solids are really more just for fun.