Yes you can do but if the najasat is for example a person had wet dream then it is makrooh to eat or drink in that state and for that it has recommended that person has to do wudhu at least before eating or drinking if he/she can’t manage Ghusl.
But make sure in the Holy month of Ramadan one can’t remain in the state of (janabat) till adhan e subh. He/she must do Ghusl before adhan otherwise his/her fast will not be valid and he/she has to pay both Qadha and Kaffara for that day fast.