With up to 18 hours a day fasted, Ramadan is not the time to be smashing PBs; but aiming to sustain active behaviour is encouraged.
Maintaining exercise activity is the key. It is certainly not the time to start on a new exercise regime so don’t be looking to up your reps, weights, distances, etc. Intense cardio sessions, plyometrics and heavy weights are not recommended to avoid strain on your body. Limiting cardio sessions to two per week may also be advisable. Your fitness levels will likely change and given the lifestyle changes this is understandable so should not be a cause for concern.
With interrupted sleep and dehydration, it can be hard to maintain a normal workout routine but finding the time to work out will help to clear your mind and keep energy levels up.