[Grammar] Clauses of Purpose

[Jacek Poland]

Which is correct?

Only drink one cup of coffee a day so as not to overstimulate your body.

Only drink one cup of coffee a day not to overstimulate your body.

 

[bhaisahab]

Which is correct?

Only drink one cup of coffee a day so as not to overstimulate your body.

Only drink one cup of coffee a day not to overstimulate your body.

I'd use the first one. The second one is OK.

 

[Jacek Poland]

I'd use the first one. The second one is OK.

Thanks! I ask because I was told the second one was incorrect, but I don't see the problem. To me, the first one does sound better though.