NOt an expert!!!
there is a thread called 'what are you giving up for lent" if you go to my profile and look at my posts you will find it. many people more knowledgable than i have posted there.
however if i recall correctly the answer is yes.
if you give up ____ for Lent, then Sunday being a FEAST day, it is an exception to the Lentan fast. and you may have it. but not “to excess” (dont stuff your face)