depends on what you are doing. dont train any other time of the day. your body needs nutrition after any exercise, drink lots of water before fasting. as much water as you can and after iftar. it'll stop you retaining fluids and always break fast with warm water or tea. your stomach will shrink whilst fasting. Avoid sugars, fatty foods esp oily ones that hold no nutrients. Ramadhaan isnt an excuse to eat naughty oods. it the time you need good quality food because you rent eating a lot