If so what are generally the lightest and harshest punishments handed down?
You can still be charged with DUI (what is commonly referred to as "less safe" DUI or a section (a)(1) DUI), even though you did not participate in the field exams. Of course, it is generally more difficult for a prosecutor to successfully charge you with DUI if you did not participate in the voluntary field exams, and it certainly opens up a broader range of possible defenses to the charge, but it is not impossiblle to be charged.
As far as sentences are concerned, it will all depend on the court involved and your history.
Criminal Defense Attorney
"Probable Cause" is all that is needed for a charge to be issued, which does not take much.
As my collegues have stated you will/may be charged as DUI 'less safe' depending upon jurisdiction if convicted, 40 hours community service,12 months probation, A&D evaluation/Treatment, fine, 24 hours minimum in custody, Unless it is reduced to a Reckless.