How can I make sweet potato fries soggy?
the reason you haven't found any recipes for soggy sweet potato fries is because of one simple fact: soggy is the default state for oven fries, unless you do something to specifically make the crispy.
So, in search of non-crispy fries, here is a list of things you could try:

Cook at a low temperature; over 400°f makes crispy fries, so closer to 350°f will prevent crisping
Don't overcook them; oven fries must first dry out before they get crispy, so to avoid that simply take out your fries as soon as they are cooked through
Don't use too much oil; oil helps fries to ... &quot;fry&quot; ... use only a little to prevent sticking
Steam your fries afterwards; after you take them out of the oven they will be very hot and will release steam, simply cover with tin foil ... a lid ... a pan ... anything
Try cooking them in the microwave instead of the oven

hope this helps
p.s.
sriracha mayonnaise is a great dip for sweet potato fries