Dehumidifier smells stinky - Frigidaire FDF70S Dehumidifier

Have you read its manual? http://manuals.frigidaire.com/prodinfo_pdf/Edison/2020266a0220en.pdf

It says (p8):

Care and Cleaning
1. Filter
a. Remove the filter every two weeks based on normal operating conditions.
b. To remove the filter, remove Bucket then pull filter downwards.
c. Wash the filter with clean water then dry.
d. Re-install the filter, then replace Bucket.
2. Cabinet
a. Dust cabinet with an oil-free cloth, or using a damp cloth.
b. Vacuum grill using brush attachment.
3. Water Bucket
a. Clean bucket with warm water and detergent.

I recommend you to use a mix 75% water, 25 % vinegar. To clean its water bucket.